Structure 1.3 – Electronic configurations

📌 Ionisation energy

• Ionisation energy is the energy required to remove an electron
• The atom must be in the gaseous state

📌 First ionisation energy

• First ionisation energy removes one electron from each atom
• One mole of gaseous 1+ ions is formed

📌 Factors affecting ionisation energy

• Nuclear charge attracts electrons towards the nucleus
• Shielding reduces the attraction of the nucleus
• Greater distance from the nucleus lowers attraction

📌 Trend across a period

• Ionisation energy increases across a period
• Nuclear charge increases
• Atomic radius decreases

📌 Trend down a group

• Ionisation energy decreases down a group
• Shielding increases
• Outer electrons are further from the nucleus

📌 Successive ionisation energies

• Each successive ionisation energy is larger
• Electrons are removed from the same shell first
• A large jump shows removal from an inner shell

Ionisation energy
↑
|        |
|        |  ← large jump
|    |
|  |
| |
|________________________→ electron removed

• The position of the jump shows the number of valence electrons