Ionisation energy is the energy to remove the first electron from an atom in the gaseous state.
- Increases across a period as electron shells go from near empty to full.
- Decreases down a group as the outer electrons become further removed from the positive nucleus.
- The second ionisation energy is always greater than the first since the electron is now being removed from a positive ion.
Electronegativity is the relative power to attract electrons.
- Increases across a period as the number of protons increases so does the positive charge of the nucleus, thus a stronger attraction and electrons are being held more tightly.
- Decrease down a group as the negatively charged electrons repel each other and the 'invaders'. The more protons, the greater the number of occupied electron shells that shield the nucleus.
- Fluorine is the most electronegative element and when combined with caesium, will react violently.
- Decreases across a period because the number of positively charged protons in the nucleus increases, pulling the negative electrons in more tightly.
- Increases down a group as the number of electron shells increase.
Melting and Boiling Points
- Increases to Group IV, then rapidly decreases.
- Groups I and II (Metallic bond). Moderate to high
- Group IV (Covalent network solids). Very high
- Group VII (Diatomic covalent). Forces between molecules are weak so it's low.
- Group VIII (Monatomic gases). Only forces between atoms are weak dispersion forces so its very low