Periodicity Flashcards

1
Q

Describe and explain the trends in melting and boiling points across period 3

A

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

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2
Q

State the type of structure shown by a crystal of silicon. Explain why the melting point of S is very high.

A

Giant covalent molecule/macromolecular structure
Strong covalent bond

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3
Q

Generally there is an increase in 1st ionisation energy across period 3. However, between Mg and Al it decreases. Explain why

A

Mg is in the S orbital but Al is in the p block, where there is slightly greater shielding

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4
Q

Generally there is an increase in 1st ionisation energy across period 3. However, between P and S it decreases. Explain why

A

S has a lower ionisation energy because the electrons start doubling up in the orbitals, therefore there is some repulsion

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5
Q

Describe and explain the trends in 1st ionisation energy across period 3

A

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

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6
Q

Why is there not an atomic radius value for Argon?

A

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

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7
Q

Describe and explain the trends in atomic radius across period 3.

A

Generally decreases (Na –> Cl)
Stronger nuclear charge across the period
Therefore stronger attraction b/wn nuclear and outer electrons –> pulls closer

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8
Q

Give the electron configuration of Silicon 14

A

1s2 2s2 2p6 3s2 3p2

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