IB Chemistry year 11 mid year exam revision

What is an orbital?

A region of space where an electron is likely to be found.

How many electrons can each orbital hold?

2 electrons with opposite spins.

What is the order of orbital filling?

1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p…

What is the shorthand electron configuration of calcium?

[Ar] 4s²

What rule requires electrons to fill lowest energy levels first?

Aufbau principle

What rule states orbitals of equal energy fill singly before pairing?

Hund's rule

Why do transition metals have variable oxidation states?

They can lose s and d electrons.

Which sublevel fills before 3d in most atoms?

4s sublevel

What is periodicity?

Repeating patterns of properties across periods or down groups.

How does atomic radius change across a period?

Decreases due to increased nuclear attraction.

How does atomic radius change down a group?

Increases due to more electron shells.

Why do cations have smaller radii than their atoms?

Loss of electrons reduces repulsion and size.

What is first ionization energy?

Energy to remove 1 mol of electrons from 1 mol of gaseous atoms.

What is the trend in ionization energy across a period?

Increases due to greater nuclear charge.

What is the trend in ionization energy down a group?

Decreases due to shielding and distance from nucleus.

What is electronegativity?

Ability of an atom to attract bonding electrons.

What trend does electronegativity follow?

Increases across a period, decreases down a group.

What is a mole?

6.022 x 10²³ particles of a substance.

What is the formula for moles?

n = m / M

What is molar mass?

The mass of one mole of a substance in g/mol.

What is the formula for concentration?

c = n / V

How is the empirical formula determined?

From the simplest whole number ratio of moles of elements.

What is the gas equation for ideal gases?

PV = nRT

What is the volume of 1 mol of gas at STP?

22.4 L

What is a limiting reagent?

The reactant that is used up first in a chemical reaction.

How do you calculate % yield?

(actual yield / theoretical yield) x 100

What is an ionic bond?

Electrostatic attraction between oppositely charged ions.

How are ions formed?

Metals lose electrons, non-metals gain electrons.

What is a lattice structure?

A regular 3D arrangement of oppositely charged ions.

Why are ionic compounds brittle?

Shifting layers align like charges, causing repulsion and breakage.

Why don't solid ionic compounds conduct electricity?

Ions are fixed in the lattice and can't move.

Why do molten or aqueous ionic compounds conduct electricity?

Ions are free to move and carry current.

How does ion size affect melting point?

Larger ions = weaker attractions = lower melting point.

How does ion charge affect lattice energy?

Higher charges = stronger attraction = higher lattice energy.

What is metallic bonding?

Attraction between a lattice of cations and delocalised electrons.

Why are metals good conductors of electricity?

Delocalised electrons move freely and carry charge.

Why are metals malleable and ductile?

Layers of ions can slide over each other without breaking bonds.

What factors strengthen metallic bonding?

More delocalised electrons and smaller cation radius.

What are alloys?

Mixtures of metals with altered properties.

Why are alloys harder than pure metals?

Different-sized atoms distort the lattice, hindering layer movement.

What determines bond character?

Electronegativity difference between atoms.

What is a polar covalent bond?

A bond where electrons are shared unequally between atoms.

What is an ionic bond in terms of electronegativity?

A bond with a large difference in electronegativity (ΔEN > 1.8).

How is bond polarity shown?

With δ⁺ and δ⁻ or a dipole arrow toward the more electronegative atom.

What is a covalent bond?

A shared pair of electrons between two atoms.

What is a coordinate bond?

A bond where both electrons come from the same atom.

What shape is CH₄?

Tetrahedral, 109.5°

What shape is NH₃?

Trigonal pyramidal, 107°

What shape is H₂O?

Bent (V-shaped), 104.5°

What type of bonding is found in diamond?

Giant covalent bonding (each C bonded to 4 others).

Why do simple covalent molecules have low melting points?

Weak intermolecular forces between molecules.

Why don't covalent compounds conduct electricity?

No free ions or electrons to carry charge.

What is absolute uncertainty?

The margin of error in a measurement (e.g. ±0.1 g).

What is percentage uncertainty?

(Absolute uncertainty / measured value) x 100%

How do you combine uncertainties when adding/subtracting?

Add the absolute uncertainties.

How do you combine uncertainties when multiplying/dividing?

Add the percentage uncertainties.

What is a systematic error?

A consistent error due to instrument flaw or method bias.

What is a random error?

An unpredictable error due to measurement limitations.

What makes a good graph?

Title, labeled axes, units, appropriate scale, line of best fit.

What is the difference between accuracy and precision?

Accuracy is closeness to true value; precision is repeatability.

What is lattice enthalpy?

Energy change when 1 mol of an ionic solid is broken into gaseous ions.

What factors increase lattice enthalpy?

Higher ionic charges and smaller radii.

Why does MgO have a higher melting point than NaCl?

Mg²⁺ and O²⁻ have higher charges, creating stronger attractions.

How does Coulomb's law relate to ionic bonding?

Force ∝ (charge₁ × charge₂) / distance²

When does ionic bonding occur?

Between metals (Group 1, 2) and non-metals (Group 16, 17) with ΔEN > 1.8

Why do Group 1 metals form +1 ions?

They lose 1 electron to achieve noble gas configuration.

Why are transition metals special in bonding?

They can form multiple ions with different oxidation states.

What is the charge of the phosphate ion?

PO₄³⁻

Name the ion: NO₃⁻

Nitrate

Name the ion: NH₄⁺

Ammonium

Name the ion: SO₄²⁻

Sulfate

Name the ion: HCO₃⁻

Hydrogencarbonate

Write the formula of calcium phosphate

Ca₃(PO₄)₂

Write the formula of ammonium nitrate

NH₄NO₃

Sodium

Na⁺

Potassium

K⁺

Calcium

Ca²⁺

Magnesium

Mg²⁺

Aluminium

Al³⁺

Silver

Ag⁺

Zinc

Zn²⁺

Iron(II)

Fe²⁺

Iron(III)

Fe³⁺

Copper(I)

Cu⁺

Copper(II)

Cu²⁺

Lead(II)

Pb²⁺

Lead(IV)

Pb⁴⁺

Tin(II)

Sn²⁺

Tin(IV)

Sn⁴⁺

Hydrogen

H⁺

Ammonium

NH₄⁺

Hydronium

H₃O⁺

Chloride

Cl⁻

Bromide

Br⁻

Iodide

I⁻

Fluoride

F⁻

Oxide

O²⁻

Sulfide

S²⁻

Nitride

N³⁻

Phosphide

P³⁻