Why are there two chlorine atoms for every magnesium atom in the compound nacl2?

Answer : Note : The formula give in the question needs to be corrected , the formula of two chlorine atoms for every magnesium atom in the compound is which is Magnesium Chloride.

Explanation : To write the formula of the compound we need to know the charge of the atoms or elements involved in the formula.

Charge of Mg is +2 and charge of Cl is -1 , to write the formula of the compound we always criss cross the charges. And also when we write the formula the total (or net) charge of the compound should be 0. Charge of Mg is +2 so to get the total(net) charge as 0 we need two Cl atoms with each -1 charge.

Mg = +2 , Cl = -1 , Cl = -1

2 Cl = -1 + (-1) = -2

Mg = +2 and 2 Cl = -2

+2 -2 = 0

So the formula for Magnesium Chloride is

given:

mass of na = 115 g

excess cl2

to determine:

mass of nacl produced

explanation:

given reaction is-

2na(s) + cl2(g) → 2nacl(s)

since cl2 is in excess, na will be the limiting reagent

as per the reaction stoichiometry na: nacl = 1: 1

i.e. moles of na reacted = moles of nacl formed

now, # moles of na = mass of na/atomic mass

                                  = 115 g/23 g.mol-1 = 5 moles

therefore, moles of nacl = 5

molar mass of nacl = 58 g/mol

mass of nacl = 5 moles * 58 g.mol-1 = 290 g

ans: amount of nacl produced = 290 g