Name the element, the higher oxide of which has the general formula RO and the relative molecular weight of 217.

Name the element, the higher oxide of which has the general formula RO and the relative molecular weight of 217. What type of chemical bond and crystal lattice does the sulfide of this element have?

1) If the formula of the higher oxide of an element is RO, then its highest valence is 2 and, therefore, this element is located in the second group of the periodic system.
2) Mr (RO) = 217, let Ar (R) = x, then x +16 = 217, hence x = 201.
3) We find in the second group of the periodic system an element with a relative atomic mass of 201 – this is Hg, that is, mercury.
4) Mercury sulfide – HgS. The molecule is formed by an ionic bond (since mercury is a metal, and sulfur is a non-metal), which means that the crystal lattice is also ionic.