periodicity

Question 1

periodic patterns of atomic radius

across the period

Answer 1

decreases across a period
* positive nuclear charge increases
* greater attractive forces between nucleus and outer shell electrons
* shielding effect stays the same

Question 2

periodic patterns of atomic radius

down the group

Answer 2

increases down the group
* positive nuclear charge increases
* shielding effect increases too
* less attractive forces between nucleus and outer shell electrons

Question 3

periodic patterns of electronegativity

across the period

Answer 3

increases across the period
* atomic radius decreases
* electrons are more attracted to the nucleus

Question 4

periodic patterns of electronegativity

down the group

Answer 4

decreases down the group
* atomic radius increases
* electrons are less attracted to the nucleus

Question 5

periodic patterns of ionisation energy

across the period

Answer 5

generally increases across the period
* atomic radius decreases
* greater attraction between nucleus and electrons
* outer shell is closer to the nucleus

Question 6

periodic patterns of ionisation energy

down the group

Answer 6

decreases down the group
* atomic radius increases
* less attraction between nucleus and electrons
* outer shell is further away from the nucleus

Question 7

highest to lowest melting point of period 3 elements

Answer 7

1. Si, silicon
2. Al, aluminium
3. Mg, magnesium
4. Na, sodium
5. S, sulfur
6. P, phosphorus
7. Cl, chlorine
8. Ar, argon

Question 8

period 3 structure and bonding

Answer 8

Na, Mg, Al :
- giant metallic structure
- metallic bonding (postive ions with mobile, delocalised electrons)

Si (and generally group 14 elements) :
- giant molecular structure
- strong covalent bond

P, S, Cl :
- simple molecular structure
- covalent bonding, weak id-id forces
- each exist as P₄, S₈, Cl₂

Ar :
- simple molecular structure
- monatomic molecule

Question 9

reaction of period 3 with Cl₂

Answer 9

Na : reacts vigorously when heated
Mg, Al : reacts vigorously
Si : reacts slowly
P : reacts slowly with excess Cl₂

Question 10

reaction of period 3 oxides with water

Answer 10

Na₂O : reacts vigorously, forming strong alkali
MgO : reacts vigorously, forming weak alkali
Al₂O₃: no reaction due to formation of protective layer
SiO₂ : no reaction due to giant molecular structure
P₄O₁₀, SO₂, SO₃ : reacts vigorously, forming acidic solution

Question 11

reaction of period 3 oxides with acid

Answer 11

Na₂O : neutralization reaction, forming salt and water
MgO :neutralization reaction, forming salt and water
Al₂O₃ : acts as base, forms salt and water

Question 12

reaction of period 3 oxides with hot, concentrated alkali

Answer 12

Al₂O₃ : acts as acid, forms salt
SiO₂ : forms salt and water

Question 13

nature of period 3 oxides

Answer 13

Na₂O : basic
MgO : basic
Al₂O₃ : amphoteric
SiO₂, P₄O₁₀, SO₂, SO₃ : acidic

Question 14

structure of period 3 oxides

Answer 14

Na₂O, MgO, Al₂O₃ : giant ionic
SiO₂ : giant covalent
P₄O₁₀, SO₂, SO₃: simple molecular

Question 15

reaction of period 3 chlorides with water

Answer 15

NaCl : dissolves to form colorless, neutral solution
MgCl₂ : dissolves to form colorless solution
Al₂Cl₆, SiCl₄, PCl₅, SCl₂ : reacts to give off white fumes of HCl gas and highly acidic solution

Question 16

structure and chemical bonding of period 3 chlorides

Answer 16

NaCl, MgCl₂ : giant ionic, ionic bonding
Al₂Cl₆, SiCl₄, PCl₅, SCl₂ : simple molecular, covalent bonding