Periodic Table(2)

Question 1

Reducing power of group 2 elements down the group

Answer 1

• down the group, standard electrode potential values becomes less positive
• reducing power of metals increases
• have higher tendency to be oxidised
• down the group, metal atoms lose their valence electrons more readily
• no. of filled principal quantum shells increases
• valence electrons are further and more shielded from the nucleus
• weaker electrostatic forces of attraction between the nucleus and the valence electrons

Question 2

Thermal decomposition of group 2 carbonates down the group

Answer 2

• down the group, ionic radius of M²⁺ increases so the charge density of the M²⁺ decreases
• M²⁺ becomes less polarising
• electron cloud of CO₃^2- anion is less distorted so the C-O covalent bond within the CO₃^2- anion is less weakened down the group
• ease of decomposition decreases, thermal stability of carbonates increases

Question 3

Real world applications of magnesium oxide, calcium carbonate, calcium oxide, barium sulfate

Answer 3

• refractory lining in high temperature furnaces because of its high melting point and low reactivity
• limestone, used in construction materials
• quicklime, sued in agriculture to overcome acidity in soil
• barium metal test in X-ray diagnostic work

Question 4

Volatility and trend down group 17

Answer 4

• measure of how readily a substance vaporises or changes from a liquid phase to a gas phase
• volatility decreases down the group, boiling point increases down the group
• halogens have simple molecular structure and are non-polar
• number of electrons in halogen molecules increases
• more energy is required to overcome the stronger id-id attractions between halogen molecules down the group

Question 5

Oxidising strength down the group

Answer 5

• oxidising power decreases down teh group
• number of filled principal quantum shells increases
• valence electrons are further and more shielded from the nucleus
• weaker electrostatic forces of attraction between the nucleus and the valence electrons
• ability of X to gain electrons decreases, hence oxidising power decreases

Question 6

Melting point of group 17 hydrides

Answer 6

• melting point generally increases
• hydrogen halides have simple molecular structure
• down the group, number of electrons in the hydrogen halide molecule increases
• strength of id-id attractions between the hydrogen halide molecules increases
• larger amount of energy is required to overcome the stronger id-id attractions between the hydrogen halide molecules

Question 7

Thermal stability down group 17

Answer 7

• decreases down the group
• valence orbital or halogen used in bonding with hydrogen is bigger and more diffused
• overlap of orbitals between the H atom and halogen is less effective
• bond energy H-F > H-Cl > H-Br > H-I
• thermal stability HF > HCl > HBr > HI

Question 8

Uses of group 17 elements, fluorine, chlorine, bromine, iodine

Answer 8

• CFC compounds are used in fire extinguishers,refrigerants
• deplete ozone later due to free radicals. Reactions
• fluorides are used in toothpaste
• water purification to kill bacteria and disinfect water due to its strong oxidising power
• manufacture of organic solvents like CCl₄
• silver bromide for photographic film
• iodine for preparation of dyes
• silver iodide in colour photography