Question & Answer: Predict the ionic formula of the compound composed of calcium and iodine. Cal_2 Ca_2l_2…..

Ans. #1. A compound composed of Calcium and Iodine

Calcium is a group-2 atom. Its ion bears a +2 charge. That is calcium ion is, Ca²⁺.

Iodine is a group-17 atom. Its ion bears a -1 charge. That is iodate ion is, I^–.

# Note that a compound is electrically neutral.

To do so-

I. Multiply the magnitude (ignore plus or minus sign) of charge on the ion to the other ion, and vice versa.

II. That, multiply the magnitude of charge on calcium ion to that of Iodine ion.

And, multiply the magnitude of charge on iodate ion to that of calcium ion.

It balances the charge on one ion to the other ion

That is, (1) x Ca²⁺ = 1Ca²⁺

(2) x I^– = 2 I^–

III. Write the relative charge on an atom (ion is written as atom in chemical formula) as sub-script that indicates number of atoms of that element in the neutral compound.

So, Ca₁ I₂.

There is no need of writing ‘1’ as subscript. It’s understood that when no numerical value is assigned to an element in a chemical formula, it’s 1.

So, Ca₁ I₂ becomes CaI₂.

Therefore, the chemical formula of compound = CaI₂.

Correct option- a. CaI₂

#2. A compound composed of potassium and phosphate.

Potassium is a group-1 atom. Potassium ion is, K⁺.

Phosphate group is (PO₄)^3-

# Note that a compound is electrically neutral.

I. Multiply the magnitude (ignore plus or minus sign) of charge on the ion to the other ion, and vice versa.

(3) K⁺ = 3 K⁺

(1) (PO₄)^3- = (PO₄)^3-

Combining the two ions give (see II, III as mentioned above)-

K₃PO₄

Therefore, the chemical formula of compound = K₃PO₄

Correct option is- b. K₃PO₄