Periodicity Set 1

Question 1

What is a group?

Answer 1

Vertical Column in the Periodic Table

Question 2

What is a period?

Answer 2

Horizontal Row in the Periodic Table

Question 3

What is periodicity

Answer 3

The study of trends in the Periodic Table

Question 4

Trend in 1st ionisation energy down group 2

Answer 4

Decreases. Despite an increase in proton number, there are more electrons, shells and shielding so less energy is needed to remove a valence electron.

Question 5

Trend in atomic radius down group 2

Answer 5

Increases. Despite an increase in proton number, there are more electrons, shells and shielding so the atomic radius is larger.

Question 6

Trend in melting point down group 2

Answer 6

Generally decreases. The type of bonding is metallic with each metal forming a 2+ cation in a sea of delocalised electrons. Down the group the larger cations mean the attraction between the nucleus of the cation and the delocalised electrons decreases.

Question 7

Trend in electronegativity down group 2

Answer 7

Decreases. Despite an increase in proton number, there are more electrons, shells and shielding so the ability of the nucleus to attract a pair of electrons in a covalent bond decreases.

Question 8

Products of reaction of barium in cold water

Answer 8

barium hydroxide + hydrogen

Question 9

What happens to pH of group 2 hydroxides down group?

Answer 9

Increases. The hydroxides become more soluble down the group so the hydroxide ion is more easily dissociated. (Alkalinity is a measure of OH ions.)

Question 10

Products of reaction of magnesium with cold water

Answer 10

magnesium hydroxide + hydrogen

Question 11

Products of reaction of magnesium with steam

Answer 11

magnesium oxide + hydrogen

Question 12

Observations for sodium and water

Answer 12

Effervescence, Na forms a ball and moves around the surface of the water. A white trail of NaOH is produced that dissolves in the water. An alkaline solution is formed

Question 13

Observations for burning Mg in air

Answer 13

White light and white powder (MgO) formed.

Question 14

How does the solubility of hydroxides change down group 2?

Answer 14

Increases - Mg(OH)2 insoluble, Ca(OH)2 sparingly soluble

Question 15

How does the solubility of sulfates change down group 2?

Answer 15

Decreases

Question 16

What is a use of barium sulfate?

Answer 16

Barium meals - a suspension of Ba(OH)2 is drunk, which coats the intestine and shows up abnormalities during an X-ray

Question 17

Chemical Test for sulfates?

Answer 17

Add acidified barium chloride. Acid reacts with carbonate impurities (causing effervescence), barium chloride reacts with sulfate forming a white ppt of barium sulfate

Question 18

What is a use of magnesium hydroxide?

Answer 18

Antacids/ indigestion medicine. The hydroxide reacts with excess stomach acid forming neutral salt and water

Question 19

What is a use of calcium hydroxide?

Answer 19

Neutralising acidic soils for growing crops

Question 20

Which acidic gas is produced from burning fossil fuels and how can it be dealt with? Include equations.

Answer 20

SO2 due to sulfur impurities in the fuel. This can cause acid rain. A calcium oxide filter is put in the flue of power stations. CaO + SO2 –> CaSO3 then CaSO3 + SO2 –> CaSO3 + CO2

Question 21

Trend in atomic radius across period 3

Answer 21

Decreases. Despite having same number of shells and shielding, the proton number increases increasing the attraction of the nucleus to the valence electrons.

Question 22

Definition of electronegativity

Answer 22

Ability of an atom to attract a pair of electrons in a covalent bond

Question 23

Trend in electronegativity across period 3

Answer 23

Increases. Despite having same number of shells and shielding, the proton number increases increasing the attraction of the nucleus to a pair of electrons in a covalent bond

Question 24

Type of bonding in Na

Answer 24

metallic

Question 25

Type of bonding in Mg

Answer 25

metallic

Question 26

Type of bonding in Al

Answer 26

metallic

Question 27

Type of bonding in Si

Answer 27

giant covalent network

Question 28

Type of bonding in P

Answer 28

P4 - simple covalent molecule

Question 29

Type of bonding in S

Answer 29

S8 - simple covalent molecule

Question 30

Type of bonding in Cl

Answer 30

Cl2 - simple covalent molecule

Question 31

Trend in melting point from Na to Al

Answer 31

Increases. The cations have an increasing charge density (smaller ions with greater charge) and an increase in delocalised electrons increases the attraction between the cations and sea of delocalised electrons

Question 32

Melting point of Si and reason

Answer 32

Very high. Si forms a giant covalent network with very strong covalent bonds between atoms requiring a lot of energy to overcome.

Question 33

Trend in melting point from P to Ar

Answer 33

S8 > P4 > Cl2 > Ar. Larger molecules have more surface area so have stronger intermolecular forces (VdWs) between molecules

Question 34

Trend in 1st ionisation energy across period 3

Answer 34

Generally increases. Despite having same number of shells and shielding, the proton number increases increasing the attraction to the electron being removed

Question 35

Account for change in 1st ionisation energy from Mg to Al

Answer 35

Decreases - the electron being lost in Al is in a 3p orbital compared to a 3s orbital in Mg, which is further from the attraction of the nucleus and is more shielded

Question 36

Account for change in 1st ionisation energy from P to S

Answer 36

Decreases - the electron being lost in S is in a doubly filled 3p orbital. There is some repulsion from the other electron so less energy is needed to remove it compared with the outer electron in P