Periodicity
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Describe and explain the trends in melting and boiling points across period 3
Increases between Na- Al - no. delocalised electrons increase, greater attraction b/w cations & electrons so ++ energy required- metallic bonding is an infinite lattice of cations held by a sea of delocalised electrons Increases to Si, as = giant covalent structure- big lattice w/ covalent bonds which require a lot of energy Decreases to Phosphorus as simple molecular, molecules held together by weak Van der Waals. Increases to Sulphur as sulphur is a larger molecule (S8 compared to P4), so larger Van der Waals. Decreases from Phosphorus to Argon as smaller molecule, same bonding
State the type of structure shown by a crystal of silicon. Explain why the melting point of S is very high.
Giant covalent molecule/macromolecular structure Strong covalent bond
Generally there is an increase in 1st ionisation energy across period 3. However, between Mg and Al it decreases. Explain why
Mg is in the S orbital but Al is in the p block, where there is slightly greater shielding
Generally there is an increase in 1st ionisation energy across period 3. However, between P and S it decreases. Explain why
S has a lower ionisation energy because the electrons start doubling up in the orbitals, therefore there is some repulsion
Describe and explain the trends in 1st ionisation energy across period 3
Generally increases but ‘jagged line’ (decrease b/w Mg and Al, and P and S) Nuclear charge increases but similar shielding Therefore needs higher energy level
Why is there not an atomic radius value for Argon?
Often values are obtained by reacting them w/ others and working out distance b/w 2 nuclei Argon doesn’t react therefore can’t work out
Describe and explain the trends in atomic radius across period 3.
Generally decreases (Na --> Cl) Stronger nuclear charge across the period Therefore stronger attraction b/wn nuclear and outer electrons --> pulls closer
Give the electron configuration of Silicon 14
1s2 2s2 2p6 3s2 3p2