Question

How to write the formula of calcium sulphate using criss-cross method?

Answer 1

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Answer 2

Answer:

The formula of calcium sulphate is CaSO₄.

Explanation:

To write the formula of calcium sulphate, first we have to know the valency of Calcium and the charge of Sulphate ion..

Ca belongs to the Group-2 in the periodic table.

Ca belongs to the Group-2 in the periodic table.It his an alkaline earth metal.

Its atomic number is 20 and it has two electrons in its outer most shell. So its valency is +2.

SO₄ ion is a polyatomic ion. Its charge is -2.

Criss Cross method:

first write the formula of Calcium and Sulphate ion (without writing sign)

Then valency of Calcium (2) is written below it and also the charge of SO₄ (2) will be written below it.

then the charge of Calcium will crossed over to SO₄ and valency of SO₄ crossed over to the Calcium being as subscript.

It will be (Ca)2(SO₄)2.

Then making them smallest. So the formula will be CaSO₄.