How to get a chemical formula

How to get a chemical formula.

So how do you get a chemical formula, this is a simple and easy way to help you form a chemical formula.

Rules before we start:

- if the compound has metals and non metals

                                                         > you always name the metal first

                                                         > remove the end of the non metal and replace it with "ide"

Step one:

- Is to find out the valency of the elements.
> This is done by looking at the periodic table.
> If your element is a metal, then the valency is the Group Number (I-VII), if your element is a non metal, the valency is the Group Number (I-VII) minus 8. (e.g Group: 5, valency is 5- 8 = -3)

Example: Element 1 is from Group 2 (all metals) therefore the valency is 2

               Element 2 is from Group 7 (non metal) therefore valency is 7 - 8 which is -1

If you have a radical, they have their own valencies. Then you use the cross method to figure out the new formula. 

Step two:

- This is simple. You just need to switch the valencies around. 

*please note that I put valencies in brackets. You don't actually, they belong above the element symbol.

Example: Element 1(2) + Element 2(-1)

Formula: Element 1 (1) Element 2 (2)

* see how the valency -1 turns into a positive, in formula you ignore the negative valency.

Example: Lead Nitrate

Symbol: Lead= Pb (2 +)

              Nitrate (radical)= NO3 (-1)

Switching: Pb (1) 

               NO3 (2)

Formula: Pb(NO3)(2) 

* again, the valency is in brackets. Usually it is on the top of the symbol.

* (2) being the valency

*Pb took the valency of NO3 and NO3 took that of Pb. Please note that Nitrate is in brackets as the 3 is part of its symbol and will stay part of it, therefore, you keep/group them together. Pb is suppose to have a (1) valency but 1 doesn't have to be included.