why do come of the compounds have a small number 2 after the symbol for chlorine?

Question

CuCI2, LiCI, CaCI2....this two is small and under cl

Answer 1

because in CaCl2 the bond is ionic and in ionic bonds you need to zero out the electrical charge and ca cation has a plus 2 charge but cl anion only has a neg one charge so it takes two cl's for every one ca to zero out charge. neg 2 and positive 2 added together equal zero.

Answer 2

The small figure '2' indicates that there are two atoms of chlorine in the molecule.
In your examples each chlorine atom is bonded to the corresponding metal atom, but the chlorine atoms are NOT bonded to each other.

However, if you have a large figure '2' as a prefix number e.g.
2CuCl2, this means that there are two molecules of CuCl2, and each molecule contains one copper(Cu) and two Chlorine(Cl) atoms. Diagrammatically, it may be shown as:-

2CuCl2 = CuCl2 + CuCl2, where each CuCl2 can be shown as 'Cl-Cu-Cl' : the line between atoms in this case only indicates which atom is combined to which atom, NOT the type of bonding.
Overall, in a chemical formula, 2CuCl2, means that there are two copper atoms and four chlorine atoms that can be used.

NB With the exception of the Noble Gases, all other gases exist as diatomic molecules, so chlorine gas would be written as 'Cl2', that is one atom of chlorine combined to another atom of chlorine (Cl-Cl).

Answer 3

This indicates that the compound is 2 Cl-'s for every Cu++, 1 Cl- for every Li+, and 2 Cl-'s for every Ca++.

Answer 4

Salts formed when chlorine bonds with a metal that has 2+ for its oxidation number.