which element do i write first?

Question

when asked to write a molecular formula for an element containing:

1) Br, C, H
2) N, C, H
3) Cl, C, H
4) N, O, H

what order do i put them in and why? thanks

Answer 1

For simple and ionic compounds its usually done in order of increasing electronegativity. For organic molecules, its usually C, then H, then whatever else in alphabetical order.
So it would be:
1. C, H, Br
2. C, H, N
3. C, H, Cl
4. H, N, O

Answer 2

You have many ways and orders to put them in.
1) Increasing/decreasing order of their atomic numbers
2) Increasing/decreasing order of their atomic weights
3) Increasing/decreasing order of their s, p, d , f orbitols.

But May be you may find the empirical formula( simplest ratio between the elements) then caluculate the molecular formula, If you know the vapour density I may help. in solving ur problem.

Answer 3

The one that is more electro-positive. The one more like a metal. Out of the three, the one that is highest and more to the left in the periodic table.