1.6- The Periodic Table

Question 1

(a)

Structure

Answer 1

Elements are arranged in order of increasing atomic number. They are positioned in vertical groups and horizontal periods.

Question 2

(b)

electronic structures of the elements and their relation to their position in the s-, p- and d blocks of the Periodic Table

Answer 2

Divided into s, p, d and f blocks.
The block denotes the subshell the elements’ valence electrons are in.

Question 3

(c)

Oxidation and reduction

Answer 3

Oxidation is loss of electrons and reduction is gain of electrons.

Question 4

(c)

Oxidising agent

Answer 4

An oxidising agent is a species that accepts electrons; it becomes
reduced itself in the process.

Question 5

(c)

Reducing agent

Answer 5

A reducing agent is a species that donates electrons; it becomes
oxidised itself in the process.

Question 6

(c)

Redox reaction

Answer 6

If the oxidation number increases, the species is oxidised; if it
decreases, the species is reduced.

Question 7

(d)

Trends in ionisation energy

Answer 7

Ionisation energy generally increases across a period due to increasing nuclear charge in the same energy level.

However, it decreases between Group 2 and Group 3 due to shielding by s-electrons and between Group 5 and Group 6 due to electron-electron repulsion in a p-orbital.

Down a group, ionisation energy decreases as increased shielding from inner electrons reduces nuclear attraction on the outer electron.

Question 8

(d)

Trends in melting temperature

Answer 8

Melting and boiling points increase from the first to the fourth element due to strong metallic or giant covalent bonding. There is then a sharp decrease at the fifth element as bonding changes to simple molecular covalent, followed by a gradual decrease to the eighth element due to weaker intermolecular forces.

Question 9

(d)

Trends in electronegativity

Answer 9

Electronegativity increases across a period because there is an
increase in nuclear charge, but the bonding electrons are always
shielded by the same inner electrons.

Question 10

(e)

reaction of Group 2 elements with oxygen

Answer 10

2X + O2 ⟶ 2XO
X is Group 2 element

Question 11

(e)

reaction of Group 2 elements with water/steam

Answer 11

X + 2H2O ⟶ X(OH)2 + H2
X is the Group 2 element.

Question 12

(f)

reactions of the aqueous cations Mg2+, Ca2+ and Ba2+ with OH‒, CO3
2‒ and SO42‒ ions

Answer 12

OH⁻: Mg²⁺ forms a slight white precipitate, while Ca²⁺ and Ba²⁺ form little to no precipitate due to increasing solubility down the group.

CO₃²⁻: All form white precipitates as their carbonates are insoluble in water.

SO₄²⁻: Mg²⁺ and Ca²⁺ form slight white precipitates, but Ba²⁺ forms a dense white precipitate as BaSO₄ is highly insoluble

Question 13

(g)

colour observed in the flame test for lithium ions

Answer 13

Red flame

Question 14

(g)

colour observed in the flame test for sodium ions

Answer 14

Orange yellow flame

Question 15

(g)

colour observed in the flame test for potassium ions

Answer 15

Lilac flame

Question 16

(g)

colour observed in the flame test for calcium ions

Answer 16

Brick red flame

Question 17

(g)

colour observed in the flame test for stronium ions

Answer 17

Crimson red flame

Question 18

(g)

colour observed in the flame test for barium ions

Answer 18

Apple green flame

Question 19

(h)

trend in general reactivity of Group 1 and Group 2 metals

Answer 19

Reactivity increases down both groups because ionisation energy decreases, making it easier for atoms to lose electrons and form positive ions. Group 1 metals are more reactive than Group 2 as they lose only one electron instead of two.

Question 20

(i)

trend in thermal stability of the Group 2 carbonates and hydroxides

Answer 20

Thermal stability increases in both as you go down the group.

Question 21

(j)

trends in solubility of Group 2 hydroxides and sulfates

Answer 21

The solubility of Group 2 hydroxides increases down the group.

The solubility of Group 2 sulfates decreases down the group

Question 22

(k)