The table shows some properties of four substances A, B, C, and D.
| Substance | Melting point in ∘C^\circ\text{C}∘C | Boiling point in ∘C^\circ\text{C}∘C | Conducts electricity when solid? | Conducts electricity when molten? |
|---|---|---|---|---|
| A | -218 | -183 | no | no |
| B | 1085 | 2562 | yes | yes |
| C | 801 | 1413 | no | yes |
| D | 1710 | 2230 | no | no |
Use the information in the table to identify the substance that: (i) is a metal (ii) has a giant covalent structure such as silicon dioxide (iii) is a gas at 25∘C25^\circ\text{C}25∘C (iv) has an ionic structure with oppositely charged ions
Some substances are compounds. What is meant by the term compound?
(i) The electronic configurations of atoms of sodium (Na) and chlorine (Cl) are:
Describe the changes in the electronic configurations of sodium and chlorine when these atoms form sodium chloride.
(ii) Calculate the relative formula mass of sodium chloride (NaCl\text{NaCl}NaCl), using the relative atomic masses: Ar(Na)=23A_r(\text{Na}) = 23Ar(Na)=23 and Ar(Cl)=35.5A_r(\text{Cl}) = 35.5Ar(Cl)=35.5.
