A sample of soil from a newly discovered cave is analyzed by a team of explorers. They find an element that is a good conductor of electricity. It also forms a chloride in the form XCl2 and an oxide in the form XO. The element is a liquid at room temperature. What is the identity of this element? Express your answer using a chemical symbol.

Hg

Explanation:

We are given information about the unknown element, and using each characteristic, we can narrow down the possible elements until we have just one possibility left.

Conducts electricity: This means that the element has to be a metal, or a semi-metal, because non-metals cannot conduct electricity.

Forming chloride and oxide ions: When it is seen that it forms chloride and oxide ions in the form of XCl₂ and XO, it can be seen that this element has an ionic charge of + 2. This narrows it down to the elements in Group 2.

Liquid at room temperature: This is tricky, because we realize that there are no elements in group 2 that are liquid at room temperature. So hence we can look at groups 3 to 12, and see if there are any liquid metals with an ionic charge of + 2.

Taking all this information into account, we can see that the only element it can be is mercury (Hg).