Chemistry Assessment 1 Yr 11

Isotopes

Atoms of the same element which have different masses, with the same number of protons but different numbers of neutrons.

Relative Atomic Mass (RAM)

The average mass of the isotopes of an element that occur naturally.

Alpha (α) Decay

Radioactive decay where a heavy nucleus (z > 82) emits an alpha particle (2 protons + 2 neutrons).

Beta (β) Minus Decay

Radioactive decay where a neutron transforms into a proton and emits an electron.

Beta (β) Plus/Positron Decay

Radioactive decay where a proton transforms into a neutron and emits a positron.

Gamma (γ) Decay

Radioactive decay where excess energy is emitted as gamma rays, which are electromagnetic radiation.

Half-life

The time it takes for the concentration of a substance to fall to half of its initial value.

Bohr Model

Atomic model where electrons are considered as particles moving in circular orbits with quantized energy levels.

Schrödinger Model

Atomic model where electrons are treated as waves, described by probability distributions in 3D volumes known as orbitals.

Ionising Radiation

Radiation that can ionize atoms by knocking out electrons, causing potential biological effects.

Atomic Radius

The distance from the center of the nucleus to the outermost electron, influenced by nuclear attraction and electron repulsion.

Electronegativity

A measure of the tendency of an atom to attract bonding electrons.

Reactivity of Metals

Metals react by losing electrons, with reactivity increasing down the group.

Reactivity of Non-metals

Non-metals react by gaining electrons, with reactivity decreasing down the group.

Opposing Forces Within an Atom

Attractive force between the nucleus and electrons balanced by repulsion between electrons.

Atomic Radius Trends

Across a period, atomic radius decreases due to increased nuclear charge attracting electrons closer. Down a group, atomic radius increases due to additional energy levels.

First Ionisation Energy Trends

Across a period, first ionization energy increases as nuclear charge increases, making it harder to remove electrons. Down a group, it decreases due to increased distance and shielding effect.

Electronegativity Trends

Electronegativity increases across a period as atoms attract bonding pairs of electrons more strongly. It decreases down a group due to increased atomic size and shielding.