Write formulas for binary ionic compounds formed from each of the following pairs of elements

Binary compounds of potassium and sulfur:

K₂S

Binary compounds of silver chlorine:

AgCl

Binary compounds of calcium and oxygen:

CaO

Binary compounds of aluminium and iodine:

AlI₃

Binary compounds of barium and nitrogen:

Ba₃ N₂

Binary compounds of sodium and selenium:

Na₂Se

Explanation:

Binary compounds:

The compounds which are made up of the atoms of only two elements are called binary compounds.

For example:

The following compounds are binary:

HCl

H₂O

NH₃

HCl is binary because it is composed of only hydrogen and chlorine. Ammonia is also binary compound because it is made up of only two elements nitrogen and hydrogen.

water is also binary because it is also made up of only two elements hydrogen and oxygen.

Binary compounds of potassium and sulfur:

K₂S

The oxidation state of potassium is +1 and sulfur is -2 so two atoms of potassium will combine with one atom of sulfur.

Binary compounds of silver chlorine:

AgCl

The oxidation state of silver is +1 and chlorine is -1. Both combine to form silver chloride.

Binary compounds of calcium and oxygen:

CaO

calcium oxide is formed by calcium and oxygen. The oxidation state of calcium is +2 and oxygen is -2.

Binary compounds of aluminium and iodine:

AlI₃

The oxidation state of aluminium is +3 and iodine is -1 so three atoms of iodine will combine with one atom of aluminium.

Binary compounds of barium and nitrogen:

Ba₃ N₂

Barium nitride is formed by barium and nitrogen. The oxidation state of nitrogen is -3 and barium is +2.

Binary compounds of sodium and selenium:

Na₂Se

The oxidation state of selenium is -2 ans sodium is +1 so two atoms of sodium will combine with one atom of selenium.

you need to take a look at the periodic system in order to sort these elements into pairs that would most likely exhibit similar chemical properties. first, you need to find elements that are found in the same group (groups are vertical in the periodic system), and then to see whether they have the same valence number. if they meet these criteria, they will have similar properties.

the first pair: ne (neon) and kr (krypton), are noble gases found in group 8

the second pair: li (lithium) and k (potassium), found in group 1

the third pair: s (sulfur) and te (tellurium), found in group 6

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.