1.2 Bonding

PRE-TEST

1. Write the electronic configurations of the following atoms, using the s, p, d, f notation.

(a) B (b) F (c) Ca (d) P (e) Ne (5)

2. Why does calcium form a cation (positive ion), Ca²⁺, whereas bromine

forms an anion (negative ion), Br^-? (2)

3. Describe, by means of a sketch and an equation in each case, the rearrangement of electrons in the formation of:

(a) sodium chloride from atoms of sodium and atoms of chlorine;

(b) chlorine molecules from chlorine atoms. (6)

4. Draw electron shell diagrams for the following:

(a) CH₄ (b) H₂O (2)

5. Draw structural formulae for the following:

(a) C₃H₈ (b) NH₃ (c) C₂H₅OH (d) C₂H₄ (4)

6. Classify each of the following according to whether their atoms are held together in:

A - simple molecules,

B - giant structures held together by covalent bonds,

C - giant structures held together by ionic bonds.

(a) carbon (as diamond), C

(b) magnesium oxide, MgO

(c) methane, CH₄

(d) potassium bromide, KBr

(e) silicon(IV) oxide (silicon dioxide, silica), SiO₂

(f) sulphur, S. (6)

7. Write formulae (not structural) for the following ions:

(a) ammonium (d) nitrate

(b) carbonate (e) sulphate

(c) hydroxide (5)

8. Classify the following changes as

A - oxidation

B - reduction

C - neither oxidation nor reduction

(a) Mg Mg²⁺ + 2e-

(b) The conversion of chlorine to chloride ions.

(c) The precipitation of lead chloride by mixing solutions containing lead ions and chloride ions.

(d) The formation of copper at the cathode during the electrolysis of copper sulphate solution.

(e) The conversion of iron(II) ions to iron(III) ions.

[Total 35 marks]