Why does the charge of one atom determine how many atoms there are of another element in a molecule?

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For example. H2O. Oxygen is a -2 charge and hydrogen (in this case) is a +1 charge. When they combine, *BECAUSE* oxygen has a -2 charge, that means there are now two hydrogens in the molecule.

Why does the charge on oxygen describe how many atoms of hydrogen there are going to be in the molecule?

My chem professor is absolutely horrible and I’m having a hard time getting this shit.

In: Chemistry

Think of it like legos. The valence electrons are a piece with a flat top (you can’t connect). But some atoms have an empty bit (either extra top bits, electrons, or extra bottom bits, positive space), so they connect together to make a full solid surface.

Oxygen has two extra connecty bits, and each hydrogen needs one connecty bit, so they connect, but the limiting factor is how many bumpy bits there are (electrons to fill the postive gaps)

It doesn’t, it determines what a stable molecule would contain. The 2 atoms of hydrogen and 1 of oxegen have to all already exist and react together to form the new molecule.

Hold on, when you say charge do you really mean oxidation number? Oxidation number is more of a theoretical charge of an atom in a molecule as opposed to an actual electric charge such as that held by an ion.

Oxygen needs 8 valence electrons to fill its outermost shell and it has 6, so if it forms 2 covalent bonds to other atoms it will achieve that. That’s why it bonds to 2 hydrogen atoms.

Also /r/chemhelp is where you need to go.

> When they combine, BECAUSE oxygen has a -2 charge, that means there are now two hydrogens in the molecule.

No! If you have one oxygen and one hydrogen when they combined they would form HO, and the oxygen would still have a -1 charge that it wants filled. When it gets another hydrogen it forms H2O and it is stable.

The charge of the oxygen isn’t making one hydrogen into two. I suspect your chemistry professor is saying that when oxygen is reacted with hydrogen (lots of oxygen atoms and lots of hydrogen atoms) it results in the pairing of H2O because oxygen’s -2 charge is fully satisfied by the +1 charge of two hydrogen atoms (in total +2) which equal out to neutral charge.