The table shows some properties of four substances W, X, Y, and Z.
| 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? |
|---|---|---|---|---|
| W | -183 | -161 | no | no |
| X | 1538 | 2862 | yes | yes |
| Y | 772 | 1423 | no | yes |
| Z | 3500 | 4827 | no | no |
Use the information in the table to identify the substance that: (i) is a metal (ii) could be diamond (iii) is a gas at 25∘C25^\circ\text{C}25∘C (iv) has an ionic structure with oppositely charged ions
Some substances are mixtures. What is meant by the term mixture?
(i) The electronic configurations of atoms of lithium (Li) and fluorine (F) are:
Describe the changes in the electronic configurations of lithium and fluorine when these atoms form lithium fluoride.
(ii) Calculate the relative formula mass of lithium fluoride (LiF\text{LiF}LiF), using the relative atomic masses: Ar(Li)=7A_r(\text{Li}) = 7Ar(Li)=7 and Ar(F)=19A_r(\text{F}) = 19Ar(F)=19.
