The Geiger–Marsden experiment provides evidence for

A.    the existence of discrete atomic energy levels.

B.     the existence of the neutron.

C.     a dense positively charged nucleus.

D.     the stability of some nuclei.

Consider the structure and bonding in ${\text{MgC}}{{\text{l}}_{\text{2}}}$ and ${\text{PC}}{{\text{l}}_{\text{3}}}$ .

Consider the molecules ${\text{PB}}{{\text{r}}_{\text{3}}}$ and ${\text{S}}{{\text{F}}_{\text{4}}}$ .

The structure of cis-but-2-ene-1,4-dioic acid is shown below.

a.i. State and explain the electrical conductivities of these two chloride compounds in their liquid state. [3]

a.ii. Suggest, giving your reasons, the approximate pH values of the solutions formed by adding each chloride compound separately to distilled water.

${\text{MgC}}{{\text{l}}_{\text{2}}}$

${\text{PC}}{{\text{l}}_{\text{3}}}$ [4]

b.i. Identify the acid-base character of the oxides of each of the elements from sodium to chlorine in period 3. [2]

b.ii. State the equations for the separate reactions of sodium oxide and phosphorus(V) oxide with water. [2]

c.i. Deduce the Lewis (electron dot) structure of both molecules. [2]

c.ii. Predict the shapes of the two molecules, giving the Br–P–Br bond angle in ${\text{PB}}{{\text{r}}_{\text{3}}}$ and the F–S–F bond angles in ${\text{S}}{{\text{F}}_{\text{4}}}$ .

[4]

c.iii. Explain why both ${\text{PB}}{{\text{r}}_{\text{3}}}$ and ${\text{S}}{{\text{F}}_{\text{4}}}$ are polar. [2]

d.i. Describe the covalent bond between carbon and hydrogen in the molecule above and how it is formed. [2]

d.ii. Deduce the hybridization of the oxygen atoms labelled $\alpha$ and $\beta$ .

$\alpha$ :

$\beta$ : [1]

d.iii. Describe sigma $(\sigma )$ and pi $(\pi )$ bonds between atoms.

$\sigma$ bond:

$\pi$ bond: [2]

d.iv. Identify the number of sigma $(\sigma )$ and pi $(\pi )$ bonds present in a molecule of cis-but-2-ene-1,4-dioic acid. [1]