2.1 Periodicity Flashcards
Periodicity
A repeating pattern of properties shown across the different periods
General trend of ionisation energy across a period
Increases
- Electrons being removed from same shell (similar sheilding)
- Increasing number of protons
- Greater nuclear attraction, so more energy required to remove an electron
Trend in atomic radius across a period
Decreases
- Same shells (similar sheilding)
- Increases protons number
- Greater nuclear attraction, so electrons held more tightly
Atomic radius –> Ionic radius
Positive ions: smaller
- Same protons attracting fewer electrons
Negative ions: larger
- Same protons attracting more electrons
Trend in electronegativity across a period
Increases
- Increasing protons
- Same shells (similar sheilding)
- So pair of electrons more strongly attracted
Structure and bonding Na to Al
Structure: Giant mettalic lattice
Bonding: Mettalic bonding
Trend in melting and boiling points Na to Al
Increases
- Charge on the ions increases
- Number of delocalised electrons increases
- Metallic bond gets stronger, so more energy required
Structure and bonding of Si
Structure: Giant covalent structure
Bonding: Covalent bonds
Melting and boiling point of Si
Very high
- Strong covalent bonds must be broken
Structure of P₄, S₈, Cl₂
Simple molecular - Weak van der Waal’s forces between molecules
Melting and boiling point order of phosphorus, sulfur and chlorine
Cl₂<P₄<S₈
- Larger molecules have more electrons
- So they have stronger van der Waal’s forces
Structure of Ar
Simple molecular - very weak van der Waal’s forces
Why does period 2 have higher first ionisation energy than period 3?
- P2 has fewer shells and less sheilding
- So stronger nuclear attraction to outer electron
Why does Al have a higher m.p than Mg?
Aluminium ions have a larger charge and more delocalised electrons (forming stronger mettalic bonds)
