Ionization Energy, EA, Electronegativity

Ionisation energy

Energy required to remove outermost electron from a species

First ionisation energy

Minimum energy required to lose one mole of electrons from one mole of gaseous atoms in the ground state

General equation

X(g) → X⁺(g) + e⁻

First ionisation energy decreases as you go…

go down a group

First ionisation energy increases as you go…

Go across a period

The greater the nuclear charge…

The smaller the atomic radius

Electron affinity (EA)

Amount of energy released when a neutral atom gains an electron to form a negatively charged ion

First electron affinity (FEA)

When a neutral atom gains an electron, energy is released

Elements with large absolute value for electron affinity

greatest tendency to gain electrons

Elements with lowest absolute value for electron affinity

Lowest tendency to gain electrons

Absolute value for FEA generally decreases

going down a group

• bc elements further down have larger atomic radius

• Outer valence shells further away from nucleus

Absolute value for FEA increases

going across a period

• elements across period have higher effective nuclear charge

• Stronger attraction between added electrons & nucleus

Electronegativity

Tendency of an atom to attract a shared pair of electrons in a covalent bond

Electronegativity value generally decreases

Down a group

• because atomic radius increases down a group from additional energy levels

Electronegativity values generally increases

Going across a period

• because effective nuclear charge increases going across a period

• Stronger attraction between nucleus & shared pair of electrons

Periodicity

General trends we observe in Periodic table for different properties