Module 1.5

• atomic radius is one-half the distance between the two nuclei in two adjacent metal atoms (metallic radius) or in a diatomic molecule (covalent radius).
• Atomic radius decreases across a period.
• Atomic radius increases down a group.
• The effective nuclear charge is the nuclear charge felt by an electron when both the actual nuclear charge and the repulsive effects of the other electrons are taken into account.
• Ionization energy increases across a period
• ionization energy decreases down a group,
• Atomic radius decreases across a period
• Atomic radius increases down a group
• lonization energy is the minimum energy required to remove an electron from a gaseous atom in its ground state.
• Electron affinity increases across a period
• Electron affinity decreases down a group