<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Nuclear Symbol Notation</title>
  <style>
    * {
      box-sizing: border-box;
      margin: 0;
      padding: 0;
    }
    body {
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      color: #1e293b;
      background: transparent;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: flex-start;
      padding: 10px;
      min-height: 100%;
      overflow-x: hidden;
    }

    .title {
      font-size: 17px;
      font-weight: 800;
      color: #0f172a;
      letter-spacing: -0.01em;
      margin-bottom: 8px;
      text-align: center;
    }

    /* Tabs for Element Selector */
    .tabs {
      display: flex;
      flex-wrap: wrap;
      justify-content: center;
      gap: 6px;
      margin-bottom: 12px;
      background: #f1f5f9;
      padding: 4px;
      border-radius: 8px;
      max-width: 100%;
    }
    .tab-btn {
      border: 1px solid transparent;
      background: transparent;
      padding: 5px 10px;
      font-size: 12px;
      font-weight: 600;
      color: #475569;
      border-radius: 6px;
      cursor: pointer;
      display: inline-flex;
      align-items: center;
      gap: 4px;
      transition: background 0.15s ease, color 0.15s ease, box-shadow 0.15s ease;
    }
    .tab-btn:hover {
      background: #e2e8f0;
      color: #0f172a;
    }
    .tab-btn.active {
      background: #ffffff;
      color: #0f172a;
      border-color: #cbd5e1;
      box-shadow: 0 1px 3px rgba(0,0,0,0.08);
    }
    .tab-nuc {
      display: inline-flex;
      align-items: center;
      font-weight: 700;
      font-size: 11px;
    }
    .tab-nuc .scripts {
      display: inline-flex;
      flex-direction: column;
      font-size: 8.5px;
      line-height: 1;
      text-align: right;
      margin-right: 1px;
    }

    /* Main Visual Layout */
    .notation-container {
      width: 100%;
      max-width: 520px;
      display: grid;
      grid-template-columns: 1fr auto 1fr;
      align-items: center;
      gap: 8px;
      margin: 4px 0 12px;
      position: relative;
    }

    .callout-col {
      display: flex;
      flex-direction: column;
      gap: 12px;
    }

    .callout-card {
      padding: 8px 10px;
      border-radius: 8px;
      font-size: 11px;
      line-height: 1.25;
      position: relative;
      display: flex;
      flex-direction: column;
      box-shadow: 0 1px 3px rgba(0,0,0,0.04);
    }

    /* Left Callouts (pointing right) */
    .callout-left {
      text-align: right;
      padding-right: 18px;
    }
    .callout-left .arrow-pointer {
      position: absolute;
      right: 4px;
      top: 50%;
      transform: translateY(-50%);
      font-size: 13px;
      font-weight: 900;
      line-height: 1;
    }

    /* Right Callouts (pointing left) */
    .callout-right {
      text-align: left;
      padding-left: 18px;
    }
    .callout-right .arrow-pointer {
      position: absolute;
      left: 4px;
      top: 50%;
      transform: translateY(-50%);
      font-size: 13px;
      font-weight: 900;
      line-height: 1;
    }

    .callout-mass {
      background: #faf5ff;
      border: 1.5px solid #c084fc;
      color: #6b21a8;
    }
    .callout-mass .arrow-pointer {
      color: #9333ea;
    }

    .callout-atomic {
      background: #f0fdfa;
      border: 1.5px solid #5eead4;
      color: #0f766e;
    }
    .callout-atomic .arrow-pointer {
      color: #0d9488;
    }

    .callout-symbol {
      background: #eff6ff;
      border: 1.5px solid #93c5fd;
      color: #1d4ed8;
    }
    .callout-symbol .arrow-pointer {
      color: #2563eb;
    }

    .label-tag {
      font-weight: 700;
      font-size: 12px;
      display: block;
      margin-bottom: 2px;
    }
    .sub-tag {
      font-size: 10.5px;
      opacity: 0.9;
      display: block;
      font-weight: 500;
    }

    /* Central Symbol Display */
    .symbol-stage {
      display: flex;
      align-items: center;
      justify-content: center;
      background: #ffffff;
      border: 2px solid #e2e8f0;
      border-radius: 12px;
      padding: 10px 14px;
      box-shadow: 0 3px 10px rgba(0,0,0,0.05);
      user-select: none;
    }
    .script-pair {
      display: flex;
      flex-direction: column;
      justify-content: space-between;
      text-align: right;
      margin-right: 6px;
      gap: 6px;
    }
    .badge-num {
      font-weight: 800;
      font-size: 22px;
      line-height: 1;
      padding: 3px 6px;
      border-radius: 6px;
      min-width: 32px;
      text-align: center;
    }
    .num-mass {
      color: #6b21a8;
      background: #f3e8ff;
      border: 1.5px solid #d8b4fe;
    }
    .num-atomic {
      color: #0f766e;
      background: #ccfbf1;
      border: 1.5px solid #99f6e4;
    }
    .badge-symbol {
      font-size: 46px;
      font-weight: 800;
      line-height: 1;
      color: #1d4ed8;
      background: #eff6ff;
      border: 1.5px solid #bfdbfe;
      border-radius: 8px;
      padding: 4px 10px;
      min-width: 60px;
      text-align: center;
    }

    /* Formula & Breakdown Box */
    .calc-card {
      width: 100%;
      max-width: 520px;
      background: #fff7ed;
      border: 1.5px solid #fdba74;
      border-radius: 10px;
      padding: 10px 12px;
      display: flex;
      flex-direction: column;
      gap: 6px;
      box-shadow: 0 1px 4px rgba(234, 88, 12, 0.06);
    }
    .calc-title {
      display: flex;
      justify-content: space-between;
      align-items: center;
      font-size: 11px;
      font-weight: 700;
      color: #c2410c;
      text-transform: uppercase;
      letter-spacing: 0.03em;
      flex-wrap: wrap;
      gap: 4px;
    }
    .calc-rule {
      font-weight: 700;
      font-size: 11px;
      color: #9a3412;
      background: #ffedd5;
      padding: 1px 6px;
      border-radius: 4px;
    }
    .equation-row {
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 6px;
      font-size: 13px;
      font-weight: 700;
      flex-wrap: wrap;
    }
    .badge-calc {
      display: inline-flex;
      align-items: center;
      padding: 3px 8px;
      border-radius: 5px;
      font-size: 12.5px;
      font-weight: 700;
      white-space: nowrap;
    }
    .bc-neutrons {
      background: #ea580c;
      color: #ffffff;
    }
    .bc-mass {
      background: #7e22ce;
      color: #ffffff;
    }
    .bc-atomic {
      background: #0f766e;
      color: #ffffff;
    }
    .math-op {
      color: #9a3412;
      font-size: 15px;
      font-weight: 800;
    }

    /* Particle Breakdown Pill Bar */
    .particle-bar {
      display: flex;
      justify-content: space-between;
      width: 100%;
      max-width: 520px;
      padding-top: 8px;
      gap: 6px;
    }
    .particle-item {
      flex: 1;
      display: flex;
      flex-direction: column;
      align-items: center;
      padding: 6px 2px;
      border-radius: 8px;
      background: #f8fafc;
      border: 1px solid #e2e8f0;
      font-size: 11px;
      font-weight: 600;
      color: #475569;
    }
    .particle-count {
      font-size: 15px;
      font-weight: 800;
      margin-top: 1px;
    }
    .p-protons {
      border-color: #99f6e4;
      background: #f0fdfa;
    }
    .p-protons .particle-count { color: #0f766e; }
    
    .p-neutrons {
      border-color: #fed7aa;
      background: #fff7ed;
    }
    .p-neutrons .particle-count { color: #ea580c; }
    
    .p-electrons {
      border-color: #bfdbfe;
      background: #eff6ff;
    }
    .p-electrons .particle-count { color: #1d4ed8; }

    @media (max-width: 420px) {
      body {
        padding: 6px;
      }
      .title {
        font-size: 15px;
        margin-bottom: 6px;
      }
      .tabs {
        gap: 4px;
        margin-bottom: 8px;
      }
      .tab-btn {
        padding: 4px 7px;
        font-size: 11px;
      }
      .notation-container {
        gap: 4px;
        margin: 2px 0 8px;
      }
      .callout-card {
        padding: 6px 6px;
      }
      .callout-left {
        padding-right: 14px;
      }
      .callout-right {
        padding-left: 14px;
      }
      .callout-left .arrow-pointer,
      .callout-right .arrow-pointer {
        font-size: 11px;
      }
      .label-tag {
        font-size: 10.5px;
      }
      .sub-tag {
        font-size: 9.5px;
      }
      .symbol-stage {
        padding: 6px 8px;
      }
      .badge-num {
        font-size: 18px;
        padding: 2px 4px;
        min-width: 26px;
      }
      .badge-symbol {
        font-size: 36px;
        padding: 2px 6px;
        min-width: 48px;
      }
      .calc-card {
        padding: 8px 10px;
        gap: 4px;
      }
      .equation-row {
        gap: 4px;
        font-size: 11px;
      }
      .badge-calc {
        font-size: 11px;
        padding: 2px 5px;
      }
      .particle-item {
        padding: 4px 1px;
        font-size: 10px;
      }
      .particle-count {
        font-size: 13px;
      }
    }
  </style>
</head>
<body>

  <div class="title">Nuclear Symbol Notation</div>

  
  <div class="tabs" role="tablist" aria-label="Element Selector">
    <button class="tab-btn active" data-index="0" role="tab">
      <span>Sodium</span>
      <span class="tab-nuc"><span class="scripts"><span>23</span><span>11</span></span>Na</span>
    </button>
    <button class="tab-btn" data-index="1" role="tab">
      <span>Carbon</span>
      <span class="tab-nuc"><span class="scripts"><span>12</span><span>6</span></span>C</span>
    </button>
    <button class="tab-btn" data-index="2" role="tab">
      <span>Chlorine</span>
      <span class="tab-nuc"><span class="scripts"><span>35</span><span>17</span></span>Cl</span>
    </button>
  </div>

  
  <div class="notation-container">
    
    <div class="callout-col">
      <div class="callout-card callout-mass callout-left">
        <span class="label-tag">Mass Number (A)</span>
        <span class="sub-tag" id="massSub">Protons + Neutrons (<span id="massSubVal">23</span>)</span>
        <span class="arrow-pointer" aria-hidden="true">➔</span>
      </div>
      <div class="callout-card callout-atomic callout-left">
        <span class="label-tag">Atomic Number (Z)</span>
        <span class="sub-tag" id="atomicSub">Protons (<span id="atomicSubVal">11</span>)</span>
        <span class="arrow-pointer" aria-hidden="true">➔</span>
      </div>
    </div>

    
    <div class="symbol-stage">
      <div class="script-pair">
        <div id="massVal" class="badge-num num-mass" title="Mass Number (A)">23</div>
        <div id="atomicVal" class="badge-num num-atomic" title="Atomic Number (Z)">11</div>
      </div>
      <div id="symbolVal" class="badge-symbol" title="Element Symbol">Na</div>
    </div>

    
    <div class="callout-col">
      <div class="callout-card callout-symbol callout-right">
        <span class="arrow-pointer" aria-hidden="true">⬅</span>
        <span class="label-tag">Element Symbol</span>
        <span class="sub-tag" id="nameVal">Sodium</span>
      </div>
    </div>
  </div>

  
  <div class="calc-card">
    <div class="calc-title">
      <span>Calculating Neutrons</span>
      <span class="calc-rule">Neutrons = A − Z</span>
    </div>
    <div class="equation-row">
      <span class="badge-calc bc-mass" id="eqA">23 (A)</span>
      <span class="math-op">−</span>
      <span class="badge-calc bc-atomic" id="eqZ">11 (Z)</span>
      <span class="math-op">=</span>
      <span class="badge-calc bc-neutrons" id="eqN">12 Neutrons</span>
    </div>
  </div>

  
  <div class="particle-bar">
    <div class="particle-item p-protons">
      <span>Protons (Z)</span>
      <span id="pCount" class="particle-count">11</span>
    </div>
    <div class="particle-item p-neutrons">
      <span>Neutrons (A−Z)</span>
      <span id="nCount" class="particle-count">12</span>
    </div>
    <div class="particle-item p-electrons">
      <span>Electrons (e⁻)</span>
      <span id="eCount" class="particle-count">11</span>
    </div>
  </div>

  <script>
    const data = [
      { name: "Sodium", symbol: "Na", a: 23, z: 11 },
      { name: "Carbon", symbol: "C", a: 12, z: 6 },
      { name: "Chlorine", symbol: "Cl", a: 35, z: 17 }
    ];

    const tabBtns = document.querySelectorAll('.tab-btn');
    const massVal = document.getElementById('massVal');
    const atomicVal = document.getElementById('atomicVal');
    const symbolVal = document.getElementById('symbolVal');
    const nameVal = document.getElementById('nameVal');
    const massSubVal = document.getElementById('massSubVal');
    const atomicSubVal = document.getElementById('atomicSubVal');
    const eqA = document.getElementById('eqA');
    const eqZ = document.getElementById('eqZ');
    const eqN = document.getElementById('eqN');
    const pCount = document.getElementById('pCount');
    const nCount = document.getElementById('nCount');
    const eCount = document.getElementById('eCount');

    function updateElement(index) {
      tabBtns.forEach((btn, idx) => {
        btn.classList.toggle('active', idx === index);
      });

      const el = data[index];
      const neutrons = el.a - el.z;

      massVal.textContent = el.a;
      atomicVal.textContent = el.z;
      symbolVal.textContent = el.symbol;
      nameVal.textContent = el.name;
      massSubVal.textContent = el.a;
      atomicSubVal.textContent = el.z;

      eqA.textContent = el.a + " (A)";
      eqZ.textContent = el.z + " (Z)";
      eqN.textContent = neutrons + " Neutrons";

      pCount.textContent = el.z;
      nCount.textContent = neutrons;
      eCount.textContent = el.z;
    }

    tabBtns.forEach((btn, idx) => {
      btn.addEventListener('click', () => updateElement(idx));
    });
  </script>
</body>
</html>

Structure of the Atom: Protons, Neutrons and Electrons

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta name="aspect-ratio" content="4:3">
  <style>
    * { box-sizing: border-box; margin: 0; padding: 0; }
    body {
      font-family: system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
      background: #f8fafc;
      color: #1e293b;
      padding: 16px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      min-height: 100%;
    }

    .wrapper {
      width: 100%;
      max-width: 480px;
      display: flex;
      flex-direction: column;
      gap: 14px;
    }

    /* Top: Nuclide Notation Card */
    .nuclide-box {
      background: #ffffff;
      border: 1px solid #e2e8f0;
      border-radius: 12px;
      padding: 12px 20px;
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 24px;
      box-shadow: 0 1px 3px rgba(0,0,0,0.04);
    }

    .symbol-display {
      display: inline-flex;
      align-items: center;
      font-size: 32px;
      font-weight: 700;
      line-height: 1;
      font-feature-settings: "tnum";
    }

    .numbers-stack {
      display: flex;
      flex-direction: column;
      font-size: 17px;
      font-weight: 700;
      text-align: right;
      margin-right: 4px;
      gap: 6px;
    }

    .num-a {
      color: #64748b;
      padding: 2px 6px;
      border-radius: 6px;
      transition: all 0.3s ease;
    }
    .num-z {
      color: #dc2626;
      padding: 2px 6px;
      border-radius: 6px;
      transition: all 0.3s ease;
    }

    .sym-k {
      font-size: 44px;
      font-weight: 800;
      color: #0f172a;
      padding-left: 2px;
    }

    /* Interactive Stepper Navigation */
    .stepper-nav {
      display: flex;
      align-items: center;
      justify-content: space-between;
      gap: 8px;
    }

    .step-pills {
      display: flex;
      gap: 6px;
      flex: 1;
    }

    .step-btn {
      flex: 1;
      border: 1px solid #e2e8f0;
      background: #ffffff;
      color: #64748b;
      padding: 6px 10px;
      border-radius: 8px;
      font-size: 13px;
      font-weight: 600;
      cursor: pointer;
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 6px;
      transition: all 0.25s ease;
    }

    .step-btn.active {
      background: #0284c7;
      color: #ffffff;
      border-color: #0284c7;
      box-shadow: 0 2px 6px rgba(2,132,199,0.25);
    }

    .play-btn {
      border: 1px solid #e2e8f0;
      background: #ffffff;
      color: #334155;
      width: 34px;
      height: 34px;
      border-radius: 8px;
      display: flex;
      align-items: center;
      justify-content: center;
      font-size: 14px;
      cursor: pointer;
      transition: all 0.2s ease;
    }
    .play-btn:active { background: #f1f5f9; }

    /* Step Breakdown Cards */
    .steps-container {
      display: flex;
      flex-direction: column;
      gap: 8px;
    }

    .step-card {
      background: #ffffff;
      border: 1px solid #e2e8f0;
      border-radius: 10px;
      padding: 10px 14px;
      display: flex;
      align-items: center;
      justify-content: space-between;
      opacity: 0.45;
      transform: scale(0.99);
      transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    }

    .step-card.active {
      opacity: 1;
      transform: scale(1);
      border-color: #cbd5e1;
      box-shadow: 0 3px 10px rgba(0,0,0,0.05);
    }

    .step-card-left {
      display: flex;
      align-items: center;
      gap: 10px;
      font-size: 14px;
      font-weight: 600;
      color: #334155;
    }

    .step-num {
      width: 22px;
      height: 22px;
      border-radius: 50%;
      background: #f1f5f9;
      color: #64748b;
      display: flex;
      align-items: center;
      justify-content: center;
      font-size: 12px;
      font-weight: 700;
    }

    .step-card.active .step-num {
      background: #0f172a;
      color: #ffffff;
    }

    .calc-expr {
      font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
      font-size: 14px;
      font-weight: 600;
      color: #475569;
    }

    .tag-val {
      font-weight: 700;
      padding: 3px 8px;
      border-radius: 6px;
      font-size: 13px;
      min-width: 32px;
      text-align: center;
    }

    .tag-protons { background: #fee2e2; color: #b91c1c; }
    .tag-electrons { background: #e0f2fe; color: #0369a1; }
    .tag-neutrons { background: #f1f5f9; color: #475569; }

    /* Bottom Summary Grid */
    .summary-grid {
      display: grid;
      grid-template-columns: 1fr 1fr 1fr;
      gap: 8px;
      margin-top: 2px;
    }

    .summary-badge {
      border-radius: 10px;
      padding: 10px 6px;
      text-align: center;
      display: flex;
      flex-direction: column;
      align-items: center;
      gap: 2px;
      transition: transform 0.25s ease;
    }

    .summary-count {
      font-size: 20px;
      font-weight: 800;
      line-height: 1.1;
    }

    .summary-label {
      font-size: 12px;
      font-weight: 600;
      text-transform: uppercase;
      letter-spacing: 0.5px;
    }

    .badge-p { background: #fef2f2; border: 1px solid #fecaca; color: #dc2626; }
    .badge-e { background: #f0f9ff; border: 1px solid #bae6fd; color: #0284c7; }
    .badge-n { background: #f8fafc; border: 1px solid #e2e8f0; color: #475569; }

    /* Highlight States */
    .highlight-red { background: #fecaca !important; color: #991b1b !important; }
    .highlight-gray { background: #e2e8f0 !important; color: #1e293b !important; }
  </style>
</head>
<body>

  <div class="wrapper">
    
    <div class="nuclide-box">
      <div class="symbol-display">
        <div class="numbers-stack">
          <span id="numA" class="num-a">39</span>
          <span id="numZ" class="num-z">19</span>
        </div>
        <div class="sym-k">K</div>
      </div>
    </div>

    
    <div class="stepper-nav">
      <div class="step-pills">
        <button class="step-btn active" onclick="setStep(0)"><span>1</span> Protons</button>
        <button class="step-btn" onclick="setStep(1)"><span>2</span> Electrons</button>
        <button class="step-btn" onclick="setStep(2)"><span>3</span> Neutrons</button>
      </div>
      <button id="playBtn" class="play-btn" onclick="togglePlay()" aria-label="Play/Pause">⏸</button>
    </div>

    
    <div class="steps-container">
      <div class="step-card active" id="card0">
        <div class="step-card-left">
          <span class="step-num">1</span>
          <span>Protons = Z</span>
        </div>
        <span class="tag-val tag-protons">19</span>
      </div>

      <div class="step-card" id="card1">
        <div class="step-card-left">
          <span class="step-num">2</span>
          <span>Electrons = Protons</span>
        </div>
        <span class="tag-val tag-electrons">19</span>
      </div>

      <div class="step-card" id="card2">
        <div class="step-card-left">
          <span class="step-num">3</span>
          <span>Neutrons = A − Z</span>
        </div>
        <div style="display: flex; align-items: center; gap: 8px;">
          <span class="calc-expr">39 − 19 =</span>
          <span class="tag-val tag-neutrons">20</span>
        </div>
      </div>
    </div>

    
    <div class="summary-grid">
      <div class="summary-badge badge-p">
        <span class="summary-count">19</span>
        <span class="summary-label">Protons</span>
      </div>
      <div class="summary-badge badge-e">
        <span class="summary-count">19</span>
        <span class="summary-label">Electrons</span>
      </div>
      <div class="summary-badge badge-n">
        <span class="summary-count">20</span>
        <span class="summary-label">Neutrons</span>
      </div>
    </div>
  </div>

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</body>
</html>

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta name="aspect-ratio" content="4:3">
  <style>
    * {
      box-sizing: border-box;
      margin: 0;
      padding: 0;
    }
    body {
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      color: #1e2945;
      background: transparent;
      padding: 8px;
      user-select: none;
      -webkit-user-select: none;
    }
    .layout {
      display: flex;
      flex-direction: row;
      flex-wrap: wrap;
      gap: 12px;
      align-items: center;
      justify-content: center;
      width: 100%;
      max-width: 680px;
      margin: 0 auto;
    }
    .atom-panel {
      flex: 1 1 240px;
      min-width: 240px;
      max-width: 320px;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      position: relative;
    }
    .svg-container {
      width: 100%;
      max-width: 260px;
      aspect-ratio: 1;
      position: relative;
    }
    svg {
      width: 100%;
      height: 100%;
      display: block;
      overflow: visible;
    }
    .cards-panel {
      flex: 1 1 240px;
      min-width: 240px;
      display: flex;
      flex-direction: column;
      gap: 8px;
    }
    .particle-card {
      border-radius: 10px;
      padding: 10px 12px;
      cursor: pointer;
      transition: box-shadow 0.2s ease, opacity 0.2s ease;
      border: 2px solid transparent;
      box-shadow: 0 1px 3px rgba(0,0,0,0.05);
    }
    .particle-card:hover {
      box-shadow: 0 3px 8px rgba(0,0,0,0.1);
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    .particle-card.active {
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    .particle-card.dimmed {
      opacity: 0.4;
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    .card-proton {
      background: #fee2e2;
      border-color: #fca5a5;
    }
    .card-neutron {
      background: #f3f4f6;
      border-color: #d1d5db;
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    .card-electron {
      background: #dbeafe;
      border-color: #93c5fd;
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      margin-bottom: 6px;
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      font-weight: 700;
      display: flex;
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      gap: 6px;
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      height: 20px;
      border-radius: 50%;
      display: inline-flex;
      align-items: center;
      justify-content: center;
      font-size: 13px;
      font-weight: 800;
      color: #ffffff;
      line-height: 1;
    }
    .sym-p { background: #dc2626; }
    .sym-n { background: #6b7280; }
    .sym-e { background: #2563eb; }

    .card-grid {
      display: grid;
      grid-template-columns: repeat(3, 1fr);
      gap: 4px;
      text-align: center;
      background: rgba(255,255,255,0.7);
      border-radius: 6px;
      padding: 6px 4px;
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    .prop-box {
      display: flex;
      flex-direction: column;
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    .prop-label {
      font-size: 11px;
      font-weight: 600;
      text-transform: uppercase;
      letter-spacing: 0.3px;
      color: #64748b;
    }
    .prop-val {
      font-size: 14px;
      font-weight: 700;
      color: #1e2945;
      margin-top: 1px;
    }
    .atom-particle {
      transition: opacity 0.25s ease, filter 0.25s ease;
    }
    .atom-particle.dimmed {
      opacity: 0.15;
    }
    .atom-particle.active {
      opacity: 1;
      filter: drop-shadow(0 0 3px rgba(0,0,0,0.5));
    }
    .shell-ring {
      stroke: #94a3b8;
      stroke-dasharray: 4 4;
      stroke-width: 1.5;
      fill: none;
      transition: stroke 0.25s ease;
    }
    .shell-ring.active {
      stroke: #2563eb;
      stroke-width: 2;
    }
  </style>
</head>
<body>
  <div class="layout">
    <div class="atom-panel">
      <div class="svg-container">
        <svg viewBox="0 0 240 240">
          
          <circle id="shell2" class="shell-ring" cx="120" cy="120" r="96" />
          <circle id="shell1" class="shell-ring" cx="120" cy="120" r="62" />

          
          <circle id="nucleus-bg" cx="120" cy="120" r="28" fill="#f8fafc" stroke="#cbd5e1" stroke-width="1.5" />

          
          <g id="neutrons" class="atom-particle">
            <circle cx="112" cy="112" r="7.5" fill="#6b7280" />
            <text x="112" y="115.5" font-size="10" font-weight="700" fill="#fff" text-anchor="middle">0</text>

            <circle cx="127" cy="114" r="7.5" fill="#6b7280" />
            <text x="127" y="117.5" font-size="10" font-weight="700" fill="#fff" text-anchor="middle">0</text>

            <circle cx="118" cy="130" r="7.5" fill="#6b7280" />
            <text x="118" y="133.5" font-size="10" font-weight="700" fill="#fff" text-anchor="middle">0</text>
          </g>

          
          <g id="protons" class="atom-particle">
            <circle cx="124" cy="107" r="7.5" fill="#dc2626" />
            <text x="124" y="111" font-size="12" font-weight="700" fill="#fff" text-anchor="middle">+</text>

            <circle cx="111" cy="124" r="7.5" fill="#dc2626" />
            <text x="111" y="128" font-size="12" font-weight="700" fill="#fff" text-anchor="middle">+</text>

            <circle cx="128" cy="126" r="7.5" fill="#dc2626" />
            <text x="128" y="130" font-size="12" font-weight="700" fill="#fff" text-anchor="middle">+</text>
          </g>

          
          <g id="electrons" class="atom-particle">
            
            <circle cx="120" cy="58" r="6" fill="#2563eb" />
            <text x="120" y="61.5" font-size="11" font-weight="800" fill="#fff" text-anchor="middle">−</text>

            <circle cx="120" cy="182" r="6" fill="#2563eb" />
            <text x="120" y="185.5" font-size="11" font-weight="800" fill="#fff" text-anchor="middle">−</text>

            
            <circle cx="216" cy="120" r="6" fill="#2563eb" />
            <text x="216" y="123.5" font-size="11" font-weight="800" fill="#fff" text-anchor="middle">−</text>
          </g>
        </svg>
      </div>
    </div>

    <div class="cards-panel">
      
      <div class="particle-card card-proton" data-target="protons">
        <div class="card-header">
          <span class="card-title">
            <span class="badge-symbol sym-p">+</span> Proton
          </span>
        </div>
        <div class="card-grid">
          <div class="prop-box">
            <span class="prop-label">Location</span>
            <span class="prop-val">Nucleus</span>
          </div>
          <div class="prop-box">
            <span class="prop-label">Charge</span>
            <span class="prop-val">+1</span>
          </div>
          <div class="prop-box">
            <span class="prop-label">Mass</span>
            <span class="prop-val">1</span>
          </div>
        </div>
      </div>

      
      <div class="particle-card card-neutron" data-target="neutrons">
        <div class="card-header">
          <span class="card-title">
            <span class="badge-symbol sym-n">0</span> Neutron
          </span>
        </div>
        <div class="card-grid">
          <div class="prop-box">
            <span class="prop-label">Location</span>
            <span class="prop-val">Nucleus</span>
          </div>
          <div class="prop-box">
            <span class="prop-label">Charge</span>
            <span class="prop-val">0</span>
          </div>
          <div class="prop-box">
            <span class="prop-label">Mass</span>
            <span class="prop-val">1</span>
          </div>
        </div>
      </div>

      
      <div class="particle-card card-electron" data-target="electrons">
        <div class="card-header">
          <span class="card-title">
            <span class="badge-symbol sym-e">−</span> Electron
          </span>
        </div>
        <div class="card-grid">
          <div class="prop-box">
            <span class="prop-label">Location</span>
            <span class="prop-val">Shells</span>
          </div>
          <div class="prop-box">
            <span class="prop-label">Charge</span>
            <span class="prop-val">−1</span>
          </div>
          <div class="prop-box">
            <span class="prop-label">Mass</span>
            <span class="prop-val">1/1840</span>
          </div>
        </div>
      </div>
    </div>
  </div>

  <script>
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    const particleGroups = {
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      electrons: document.getElementById('electrons')
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        if (!selected) {
          card.classList.remove('active', 'dimmed');
        } else if (cardTarget === selected) {
          card.classList.add('active');
          card.classList.remove('dimmed');
        } else {
          card.classList.remove('active');
          card.classList.add('dimmed');
        }
      });

      Object.entries(particleGroups).forEach(([key, group]) => {
        if (!selected) {
          group.classList.remove('active', 'dimmed');
        } else if (key === selected) {
          group.classList.add('active');
          group.classList.remove('dimmed');
        } else {
          group.classList.remove('active');
          group.classList.add('dimmed');
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      shells.forEach(shell => {
        shell.classList.toggle('active', selected === 'electrons');
      });

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          nucleusBg.setAttribute('stroke', '#64748b');
          nucleusBg.setAttribute('stroke-width', '2');
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          nucleusBg.setAttribute('stroke-width', '1.5');
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    Object.entries(particleGroups).forEach(([key, group]) => {
      group.style.cursor = 'pointer';
      group.addEventListener('click', () => {
        applySelection(key);
      });
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  </script>
</body>
</html>

UK-GCSE-SCIENCE-PHYS-AST-01-04

Aligned learning resources

Related diagrams