IB HL Chemistry Semester 1 Revision Booklet

Vocabulary terms and definitions from the IB HL Chemistry dense revision booklet for semester 1, covering atomic theory, bonding, energetics, and kinetics.

Diffusion

The net movement of particles from high to low concentration.

Temperature

A measure that is proportional to the average kinetic energy of particles.

Proton

A subatomic particle with a charge of $+1$ and a mass of $1$.

Neutron

A subatomic particle with a charge of $0$ and a mass of $1$.

Electron

A subatomic particle with a charge of $-1$ and a mass of $\frac{1}{1836}$.

Atomic number

The number of protons in an atom.

Mass number

The total number of protons and neutrons in an atom.

Isotopes

Atoms with the same number of protons but different numbers of neutrons.

Relative atomic mass

The weighted mean isotopic mass of an element.

Mass spectrometry

A technique involving the stages: ionisation $\rightarrow$ acceleration $\rightarrow$ deflection $\rightarrow$ detection.

Valence electrons

Electrons in the outer shell that determine an element's chemistry.

Shell boundaries

Indicated by successive ionisation energy jumps.

Cations

Positively charged ions formed by losing electrons from the highest energy level first.

Mole (mol)

$1\,mol$ is equal to $6.022 \times 10^{23}$ particles.

Empirical formula

The simplest ratio of atoms of each element in a compound.

Molecular formula

The actual ratio of atoms of each element in a compound.

Limiting reagent

The reactant that is consumed first in a chemical reaction.

Percentage yield

$$\frac{\text{actual}}{\text{theoretical}} \times 100$$

Atom economy

$$\frac{\text{useful products}}{\text{total products}} \times 100$$

Ideal Gas Law

$$PV = nRT$$

Ideal gases

Gases that have negligible volume and no intermolecular forces; real gases deviate at high pressure and low temperature.

Ionic Bonding

The electrostatic attraction between oppositely charged ions in giant ionic lattices.

Covalent bond

A shared pair of electrons between atoms.

VSEPR: Linear

A molecular geometry with a bond angle of $180^{\circ}$.

VSEPR: Trigonal planar

A molecular geometry with a bond angle of $120^{\circ}$.

VSEPR: Tetrahedral

A molecular geometry with a bond angle of $109.5^{\circ}$.

VSEPR: Trigonal pyramidal

A molecular geometry with a bond angle of $107^{\circ}$.

VSEPR: Bent

A molecular geometry with a bond angle of $104.5^{\circ}$.

Metallic Bonding

Positive ions in a sea of delocalised electrons, explaining conductivity, malleability, and ductility.

Condensation polymerisation

A process that links monomers while removing small molecules.

Atomic radius trend

Decreases across a period due to increased nuclear charge without increased shielding.

Ionisation energy trend

Generally increases across a period due to nuclear charge, shielding, and distance changes.

Exothermic

A reaction where $\Delta H$ is negative and energy is released.

Endothermic

A reaction where $\Delta H$ is positive and energy is absorbed.

Activation energy ($E_a$)

The minimum energy required for a reaction to occur.

Hess's Law

The enthalpy change of a reaction is independent of the route taken.

Bond enthalpy calculation

$$\Delta H = \text{bonds broken} - \text{bonds formed}$$

Energy density

The amount of energy released per unit mass or volume of a fuel.

Rate equation

$$\text{rate} = k[A]^m[B]^n$$

Dynamic equilibrium

A state where the forward and reverse reaction rates are equal.

Le Châtelier's principle

Predicts shifts in equilibrium caused by changes in concentration, pressure, and temperature.

Free-radical substitution

A reaction occurring in three stages: initiation, propagation, and termination.

Radicals

Highly reactive species containing unpaired electrons.