All of inorganic chemistry 1

What is periodicity?

The repeating trends in properties of elements across periods in the periodic table, caused by increasing nuclear charge.

How does atomic radius change across a period and down a group?

• Across a period: decreases (increasing nuclear charge pulls electrons closer)

• Down a group: increases (more electron shells)

How does first ionisation energy change across a period and down a group?

• Across a period: increase (more nuclear charge, same shielding)

• Down a group: decreases (more shells → more shielding)

How does electronegativity change across a period and down a group?

• Across a period: increases

• Down a group: decreases

What is the trend in melting points across period 3?

• Increases from Na → Mg → Al (metallic bonding strengthens)

• Then drops at Si (giant covalent)

• Then very low doe P, S, Cl, Ar (simple molecular)

What is the trend in reactivity of Group 2 metals?

Increases down the group (atomic radius increases → easier to lose outer electrons)

What is the trend in melting points of Group 2 metals?

Generally decreases down the group (metallic bonding weakens as atoms get bigger)

What is the trend in solubility of Group 2 hydroxides (M(OH)2)?

• Increases down a group.

• E.g.:

  • Mg(OH)2 - sparingly soluble

  • Ba(OH)2 - very soluble

What is the trend in solubility of Group 2 sulfates (MSO4)?

• Decreases down the group.

• E.g.:

  • MgSO4 - soluble

  • BaSO4 - insoluble

How are Group 2 compounds used in everyday life?

• Mg(OH)2 : antacid

• CaCO3 : building material, neutralises acid in soil

• BaSO4 : barium meal for X-rays (insoluble)

What are halogens?

Group 7 elements

What is the trend in reactivity of halogens?

Decreases down the group (atoms get larger → outer electrons further from nucleus → harder to gain electrons)

What is the trend in melting and boiling points of halogens?

Increases down the group (larger molecules → stronger van der Waals forces)

What is the trend in electronegativity in halogens?

Decreases down the group (harder to attract electrons)

What is the trend in oxidising power in halogens?

Decreases down the group (fluorine strongest, iodine weakest)

Give the trend in solubility of halogens in water and organic solvents

• Water:

  • Soluble: F2, Cl2

  • Slightly soluble: Br2

  • Very low solubility: I2

• Organic solvent:

  • solubility increases down the group

What is a halogen displacement reaction?

A more reactive halogen displaces a less reactive halide from solution.

What is the colour of halogens in solution?

• F2: pale yellow (gas)

• Cl2: green (gas)

• Br2: orange (solution)

• I2: brown (solution)

Are halogens oxidising or reducing agents?

Oxidising agents (they get reduced themselves)

What happens in a halogen-halide displacement reaction in terms of redox?

• Halogen is reduced (gains electron)

• Halide ion is oxidised (loses electron)

How are Group 2 metals used in agriculture?

Ca(OH)2 neutralises acidic soils.

How are halogens used in everyday life?

• Cl2: water purification

• Br2: flame retardants

• I2: antiseptics