Chemistry Help, Covalent Bonding, again please lol?

Question

hi, in a bond like H2O2 or SOs, H, or S can only share 2 electrons. But the other elemnt, such as the two oxygens need 4 electrons. the same with O2, it needs 4 electrons but S can only give 2, what would be the Lewis Dot structure and how would they form a bond? With a single, douple or triple bond?

Answer 1

Ok - let's take a step back here.

When atoms come together to form a molecule, they bring with them however many valance electrons they have. All of these valance electrons could potentially be used for bonding. There is no limit to how many valence electrons can be used for bonding. There are, however a finite number of valance electrons for each atom.

To determine the number of valance electrons an atom has, we look at the periodic table. Here's one:
http://www.webelements.com/
Accross the top, the group numbers are listed. On the left side (the blue elements) the valance electrons are equal to the group number of that column. On the right side (the yellow elements) the valence electrons are equal to 10-the group number. So B has 3 and S has 6 and F has 7. Ok?

So to get back to your question. H and S won't only share 2 electrons. H will share 1 because it only has 1 electron, and S could possibly share 6 because that's how many valance electrons it has. It's true that the two oxygens need 4 elelctrons. Each oxygen has 6 valance electrons when it wants to have 8. So each oxygen wants 2 extra electrons.

For H2O2, hydrogen peroxide: all single bonds

H-O-O-H

with 2 lone pairs on each of the oxygens.

Here's a site that might help you out a little:
http://www.stolaf.edu/depts/chemistry/courses/toolkits/123/js/lewis/