[earthnation112]

Thank you for the reply, the examples you gave were very clear and helped make the issue more understandable. The chemguide link really helped might order the book was really impressed with the clarity of the information supplied, and the link to chemwiki was exactly what I was after. The issue I was having was when you mentioned “What are the pure elements (and their states) that make up the compound CH3Cl”

I was getting confused to why it was the following:
2C(s) + 3H_2(g) + Cl_2 (g) --------- 2CH_3Cl

And not:

2C(s) + 3H_2(g) + 2Cl (g) --------- 2CH_3Cl
I’m guessing that Cl being a diatomic molecule is the reason it can’t exist as 2Cl, but I was wondering how this applies to all the other elements and what the rules are.

[mikasaur]

Glad it makes sense.

Unless anyone else can chime in with a better idea, you kind of just have to know. With most elements that you find in organic molecules, they're diatomic gaseous molecules at standard conditions. H₂, O₂, N₂, Cl₂. Carbon is graphite.

As you learn more chemistry you may get a better "feel" for why. Molecular orbital theory helps explains why nitrogen LOVES to make N≡N. And why carbon likes to make graphite. And why N₂ is a gas while graphite is a solid at standard conditions.

For now I guess it's just something you'll have to memorize.

[earthnation112]

No worries thanks for the input, guess I will try more practice questions and just get better at it and more experience.