Chemistry 2 (Grade 11)
Electrons and the periodic table, ionic, covalent and metallic bonding, stoichiometry, states of matter and gases.
Electrons and the periodic table, ionic, covalent and metallic bonding, stoichiometry, states of matter and gases.
Units of the book
| Unit | What to know |
|---|---|
| Electrons in atoms | light and quanta, quantum theory, electron configuration |
| The periodic table | its history, classifying elements, periodic trends |
| Ionic compounds and metals | ion formation, formulas and names, metallic bonding |
| Covalent bonds | naming, structures, VSEPR shapes, polarity |
| Stoichiometry | empirical and molecular formulas, hydrates, limiting reactant, yield |
| States of matter | kinetic theory, intermolecular forces, changes of state |
| Gases | Boyle, Charles, Gay-Lussac, combined and ideal gas laws |
Formulas to remember
- 1s 2s 2p 3s 3p 4s 3d: Aufbau order
- s:2 p:6 d:10 f:14: sublevel capacity
- P₁V₁ = P₂V₂: Boyle’s law
- V₁/T₁ = V₂/T₂: Charles’s law
- PV = nRT: ideal gas
- 22.4 L/mol: molar volume (STP)
- ΔEN > 1.7: ionic bond
- 0.4 – 1.7: polar covalent
🧠 Memory kit: Chemistry 2 formulas
| Formula | In plain words | How to remember it |
|---|---|---|
| c = λν, E = hν | Light: speed = wavelength × frequency; quantum energy = Planck × frequency. | Wavelength and frequency are opposite; energy rises with frequency. |
| 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p | The order sublevels fill (Aufbau). | Write rows 1s / 2s 2p / 3s 3p 3d / 4s 4p 4d 4f … and draw diagonal arrows from top-right to bottom-left. |
| s: 2, p: 6, d: 10, f: 14 | How many electrons each sublevel holds. | They go up by 4: orbitals 1, 3, 5, 7, with two electrons each. |
| 2n² | Most electrons in main level n. | n = 1 → 2, n = 2 → 8, n = 3 → 18. |
| P₁V₁ = P₂V₂ | Boyle’s law (constant temperature): pressure and volume are opposite. | Squeeze a balloon → it shrinks. |
| V₁ / T₁ = V₂ / T₂ | Charles’s law (constant pressure): volume goes with temperature in kelvin. | A balloon in the sun grows. |
| P₁ / T₁ = P₂ / T₂ | Gay-Lussac’s law (constant volume). | Tyre pressure rises on a hot day. |
| P₁V₁ / T₁ = P₂V₂ / T₂ | The combined gas law. | It holds all three laws: cross out what stays constant. |
| PV = nRT, R = 0.0821 L·atm/(mol·K) | The ideal gas law. | Read it “piv = nert”. R = 8.31 J/(mol·K) in SI units. |
| STP: 0 °C (273 K), 1 atm, 22.4 L/mol | Standard conditions: one mole of any gas fills 22.4 L. | Moles = volume ÷ 22.4. |
| rate₁ / rate₂ = √(M₂ / M₁) | Graham’s law: lighter gases spread faster. | The masses go upside down under the root. |
| النسبة المئوية للمردود = (الفعلي / النظري) × 100 | Percent yield. | Actual is what you got; theoretical is what the equation predicts. |
| ΔEN: 1.7 | Bond type from electronegativity difference: nonpolar covalent, polar covalent, ionic. | Small gap → fair sharing; big gap → the electron is taken. |
🧠 Memory kit: the periodic table, bonds and shapes
| Topic | What to know |
|---|---|
| Atomic radius | grows down a group (more levels) and to the left across a period. |
| Ionization energy and electronegativity | rise up and to the right. Fluorine is the most electronegative (3.98); caesium and francium the least. Noble gases have the highest ionization energies. |
| Groups | 1 alkali metals, 2 alkaline earth metals, 3–12 transition metals, 17 halogens, 18 noble gases. |
| Valence electrons | group 1 → 1, group 2 → 2, groups 13–18 → group number − 10. |
| Ion charges | group 1: +1, 2: +2, 13: +3, 15: −3, 16: −2, 17: −1. Metals lose electrons; non-metals gain. |
| Polyatomic ions | NH₄⁺ ammonium, OH⁻ hydroxide, NO₃⁻ nitrate, SO₄²⁻ sulfate, CO₃²⁻ carbonate, PO₄³⁻ phosphate, HCO₃⁻ hydrogen carbonate. |
| Filling rules | Aufbau: lowest energy first. Pauli: at most two electrons per orbital, opposite spins. Hund: one electron in each orbital before pairing. Exceptions: Cr: [Ar] 3d⁵ 4s¹ and Cu: [Ar] 3d¹⁰ 4s¹. |
| VSEPR shapes | 2 bonding pairs → linear 180° (sp), 3 → trigonal planar 120° (sp²), 4 → tetrahedral 109.5° (sp³), 3 + 1 lone pair → trigonal pyramidal 107° (NH₃), 2 + 2 lone pairs → bent 104.5° (H₂O). |
| Forces between molecules | weakest to strongest: dispersion (London) → dipole–dipole → hydrogen bonds (H with N, O or F). Stronger forces → higher boiling point. |
| Metallic bonding | a “sea of electrons” around positive ions, which is why metals conduct and can be hammered and drawn. |
- Trends in one word: “fluorine”. Ionization energy and electronegativity grow towards fluorine (top right); radius and metallic character grow away from it (bottom left).
- Hybridization by counting: count electron groups on the central atom (bonds + lone pairs): 2 → sp, 3 → sp², 4 → sp³. The power is the count − 1.
- Boyle and Charles: “Boyle squeezes” (P and V opposite), “Charles heats” (V and T together). Gas-law temperatures are always in kelvin.
A way of memorizing that sticks
- Understand before you memorize: read “in plain words” for each formula and say out loud what it measures and why each quantity is multiplied or divided. A formula you understand takes a minute to learn.
- Active recall: cover the formula column and write it from memory, then check. Writing from memory beats rereading by far.
- Spaced repetition: review the same sheet after 1 day, 3 days, a week and two weeks. Four short reviews lock it in until test day.
- Your own formula page: write every formula of a book on one page by hand. If it does not fit, you are writing things you can derive, so cut them.
- Teach it: explain the formula to a friend, or to yourself in a mirror, in two sentences. If you cannot explain it, you do not know it yet.
- Use it at once: after each group, press “Try one” in the patterns below. Memory sets when you use it.
Question patterns
Configuration and position
The highest shell = period; valence electrons give the group.
Periodic trends
Radius falls across and rises down; ionization energy and electronegativity do the opposite.
Ionic formulas
Make the charges add to zero (criss-cross); put polyatomic ions in brackets.
Bonds and shapes
Single σ; double σ+π; triple σ+2π. CH₄ tetrahedral, NH₃ pyramidal, H₂O bent, CO₂ linear.
Stoichiometry
Use the coefficients of the balanced equation as mole ratios.
Gas laws
Always use kelvin.
Ideal gas
PV = nRT with R = 0.0821
More patterns (figures and calculations)
Hydrogen spectral series
Lyman (n = 1) UV, Balmer (n = 2) visible, Paschen (n = 3) infrared.
Lattice energy
Bigger charges and smaller ions → higher energy.
Valence electrons and bonds
Group 15 → 3 bonds, 16 → 2, 17 → 1.