Please help . also need the name of their binary ionic compound .

See below!

Explanation:

For the chemical formula, you need to have enough of each atom so that the charge is zero.

Aluminum has a +3 charge, and fluorine has a -1 charge.  Since the charge has to be zero, you need three fluorines, giving you AlF₃.

Barium has a +2 charge, and oxygen has a -2 charge.  Since the charges are equal in magnitude but opposite in sign, you only need one of each atom giving you BaO.

The name of the ionic compound will be the metal and then the nonmetal.  When putting the nonmetal in, change the ending to "-ide".  For example "chlorine" would be "chloride.

CaCl₂  ==>  calcium chloride

Ga₂S₃  ==>  gallium sulfide

K₃N  ==>  potassium nitride

AlF₃ ==>  aluminum fluoride

BaO  ==>  barium oxide

every chemical equation adheres to the law of conservation of mass, which states that matter cannot be created or destroyed. therefore, there must be the same number of atoms of each element on each side of a chemical equation.