⚛️ Chemistry Fundamentals Lab
Master Atomic Structure • Periodic Table • Valency • Molecular Formulas • Equations
Interactive Learning for Ages 14-16
⚛️ Atomic Structure (Z = 1-20)
Key Concept: An atom consists of a central nucleus (protons + neutrons) surrounded by electrons in shells. The atomic number (Z) equals the number of protons. Mass number (A) = Protons + Neutrons.
📍 Select an Element (First 20 Elements)
💡 Study Tip: Notice how electrons fill shells according to the pattern 2, 8, 8. The outermost shell electrons determine chemical properties!
📊 Modern Periodic Table (First 20 Elements)
Periodic Law: Properties of elements repeat in a periodic manner when arranged by atomic number. Elements in the same group have similar properties.
🎯 Interactive Periodic Table
🟨 Metals
Good electrical conductors, shiny, malleable, ductile
🔵 Non-metals
Poor conductors, brittle or gaseous, dull appearance
📈 Trends in Periodic Table
Atomic Size
↓ Decreases left to right in a period
↑ Increases top to bottom in a group
↑ Increases top to bottom in a group
Metallic Character
↓ Decreases left to right
↑ Increases down a group
↑ Increases down a group
Valency
Remains same in a group
Changes across a period
Changes across a period
📋 Periodic Table Information
| Period | Number of Shells | Element Range | Examples |
|---|---|---|---|
| 1st Period | 1 | Z = 1-2 | H, He |
| 2nd Period | 2 | Z = 3-10 | Li, Be, B, C, N, O, F, Ne |
| 3rd Period | 3 | Z = 11-18 | Na, Mg, Al, Si, P, S, Cl, Ar |
| 4th Period | 4 | Z = 19-20 | K, Ca |
💡 Memory Trick: “NAASL” = Non-metals are on the right side (N, O, F, S, Cl). Metals are on the left side!
🔗 Valency of Elements (Z = 1-20)
Definition: Valency is the number of electrons an atom loses, gains, or shares to achieve a stable electron configuration (usually 8 electrons in the outermost shell = Octet Rule, except H, He with 2).
🎯 Valency by Group
Group 1
1
H, Li, Na, K (1 valence e⁻)
Group 2
2
Be, Mg, Ca (2 valence e⁻)
Group 13
3
B, Al (3 valence e⁻)
Group 14
4
C, Si (4 valence e⁻)
Group 15
3
N, P (5 valence e⁻)
Group 16
2
O, S (6 valence e⁻)
💡 How to Determine Valency
Step 1: Electron Config
Write the electron configuration to find valence electrons
Step 2: Count Outermost
Count electrons in the outermost shell
Step 3: Compare with 8
Usually aim for 8 (octet rule) or 2 for H, He
📊 Complete Valency Table
| Element | Symbol | Atomic No. | Electron Config | Valency |
|---|---|---|---|---|
| Hydrogen | H | 1 | 1 | 1 |
| Carbon | C | 6 | 2, 4 | 4 |
| Nitrogen | N | 7 | 2, 5 | 3 |
| Oxygen | O | 8 | 2, 6 | 2 |
| Sodium | Na | 11 | 2, 8, 1 | 1 |
| Chlorine | Cl | 17 | 2, 8, 7 | 1 |
| Calcium | Ca | 20 | 2, 8, 8, 2 | 2 |
💡 Quick Rule: Group number usually tells valency (Groups 1-3 lose electrons, Groups 15-17 gain electrons). Noble gases (Group 18) have valency 0!
🧬 Molecular Weight & Formulas
Molecular Weight (MW): Sum of atomic weights of all atoms in a molecule. It tells us the mass of one molecule and is crucial in chemical calculations.
📍 Molecular Formula – Definition
What is Molecular Formula?
It shows the exact number of each type of atom in a molecule. For example, H₂O has 2 hydrogen atoms and 1 oxygen atom.
🧮 Common Molecular Weights
H₂O
Water
18
CO₂
Carbon Dioxide
44
NaCl
Salt
58.5
H₂SO₄
Sulfuric Acid
98
NH₃
Ammonia
17
CH₄
Methane
16
Ca(OH)₂
Calcium Hydroxide
74
CaCO₃
Calcium Carbonate
100
📚 How to Write Molecular Formulas
Rule 1: Find Valencies
Determine valency of each element
Rule 2: Crisscross
Write valency as subscript (crisscross method)
Rule 3: Simplify
Simplify if subscripts have common factors
📝 Examples of Formula Writing
NaCl (Sodium Chloride)
Na⁺ (valency 1) + Cl⁻ (valency 1) = NaCl
CaCO₃ (Calcium Carbonate)
Ca²⁺ + CO₃²⁻ = CaCO₃
Al₂O₃ (Aluminum Oxide)
Al³⁺ (valency 3) + O²⁻ (valency 2) = Al₂O₃
🧮 Step-by-Step MW Calculation
Example: Calculate MW of H₂SO₄
Step 1: Identify atoms → 2 H + 1 S + 4 O
Step 2: Find atomic masses → H=1, S=32, O=16
Step 3: Multiply → (2×1) + (1×32) + (4×16) = 2 + 32 + 64
Step 4: Add → MW = 98
Step 2: Find atomic masses → H=1, S=32, O=16
Step 3: Multiply → (2×1) + (1×32) + (4×16) = 2 + 32 + 64
Step 4: Add → MW = 98
📊 Atomic Mass Reference Table
| Element | Symbol | Atomic Mass | Element | Symbol | Atomic Mass |
|---|---|---|---|---|---|
| Hydrogen | H | 1 | Sodium | Na | 23 |
| Carbon | C | 12 | Magnesium | Mg | 24 |
| Nitrogen | N | 14 | Aluminum | Al | 27 |
| Oxygen | O | 16 | Silicon | Si | 28 |
| Sulfur | S | 32 | Chlorine | Cl | 35.5 |
| Calcium | Ca | 40 | Iron | Fe | 56 |
⚖️ Chemical Equations & Balancing
Chemical Equation: A symbolic representation of a chemical reaction. Must always be balanced – the number of atoms of each element must be equal on both sides (Law of Conservation of Mass).
📝 Types of Equations
Word Equation
Uses names of substances. Example: Magnesium + Oxygen → Magnesium Oxide
Unbalanced Formula
Uses symbols but atoms don’t match. Fe + O₂ → FeO (not balanced)
Balanced Formula
Equal atoms on both sides. 4Fe + 3O₂ → 2Fe₂O₃ (balanced)
⚖️ Unbalanced vs Balanced Equations
❌ Unbalanced
Fe + O₂ → FeO
Fe: 1 left, 1 right ✓
O: 2 left, 1 right ✗
O: 2 left, 1 right ✗
✓ Balanced
4Fe + 3O₂ → 2Fe₂O₃
Fe: 4 left, 4 right ✓
O: 6 left, 6 right ✓
O: 6 left, 6 right ✓
🔧 Steps to Balance Equations
- Write unbalanced equation using correct formulas
- List all atoms on both reactant and product sides
- Count atoms of each element on both sides
- Balance one element at a time by adding coefficients
- Verify all atoms are equal on both sides
- Use smallest whole numbers as coefficients
📋 Important Chemical Equations
🔥 Hydrogen burns in Oxygen
2H₂ + O₂ → 2H₂O
CombustionProduct: Water
🔥 Magnesium burns
2Mg + O₂ → 2MgO
CombustionBright light!
💨 Carbon burns
C + O₂ → CO₂
CombustionGreenhouse gas
🌫️ Sulfur burns
S + O₂ → SO₂
CombustionPungent smell
⚗️ HCl + NaOH Reaction
HCl + NaOH → NaCl + H₂O
NeutralizationAcid-Base
🟠 Copper reacts with Oxygen
2Cu + O₂ → 2CuO
OxidationBlack powder
💡 Key Points: Always use the correct formulas first! Never change subscripts in formulas. Only change coefficients (numbers in front). Check your work by counting atoms!
❓ Multiple Choice Questions
Test your understanding! Click on an option to see if you’re correct. Then click “Show Explanation” to learn more.
📚 Long Answer Questions
Read the questions carefully and click to see detailed answers with explanations.
⚛ Atomic Structure & Periodic Table Learning Hub
Master Atomic Structure, Valency, Periodic Table and Chemical Formula through visual learning, simulations and practice activities.
Chapter Roadmap
Atomic Structure Visual Lab
Electron Configuration Game
Click “Add Electron” to fill shells (K=2, L=8, M=8, N=2). Try Na = 2,8,1
K Shell
0/2L Shell
0/8M Shell
0/8N Shell
0/2Valency Master (First 20 Elements)
✨ Click any element to see details
Modern Periodic Table (First 20)
Click element to see properties
Modern Periodic Law: Properties of elements are periodic functions of their atomic number.
Periodic Trends (Click Cards)
📏 Atomic Size
🔩 Metallic Character
🔄 Shells
⚡ Valency Trend
Formula Builder Game
Click on any compound button, type the correct formula!
🏆 Score: 0/6
Molecular Weight Calculator
⚖️ Chemical Equation Balancer Challenge
H₂ + O₂ → H₂O
📘 Quick Revision Notes
📝 MCQ Practice Zone (30 Questions)
Score: 0/30 Q1/30
✅ True / False Challenge (15 Questions)
Score: 0/15
🔗 Match The Following
Match column A with column B:
1. Proton -> a) Negative charge
2. Neutron -> b) Positive charge
3. Electron -> c) Neutral
📌 Short & Long Questions (Click to reveal answers)
⭐ Exam Guess Questions (SEE Style)
🧠 Memory Tricks & Mnemonics
First 20: “He Has Light Brain But Can Not Offer Full Nine” (H,He,Li,Be,B,C,N,O,F,Ne,Na,Mg,Al,Si,P,S,Cl,Ar,K,Ca)
Valency of Group 1: +1, Group 2: +2, Group 17: -1
Formula Writing: Criss-cross valencies
✨ Fun Facts
💧 Water expands when freezes
⚛️ Most elements are metals
🧪 Helium doesn’t freeze at absolute zero
🏅 Achievement System
🥉 Beginner Chemist 🥈 Atomic Explorer 🥇 Periodic Table Master