Exercises: How molecular compounds form

In the water molecule (H₂O), oxygen shares electrons with two hydrogen atoms. Explain what "sharing electrons" means and how it differs from what happens in an ionic compound such as table salt.

In carbon dioxide (CO₂) carbon shares electrons with two oxygens, and in methane (CH₄) it shares with four hydrogens. How many shared electron pairs does carbon have in each molecule? Explain why in both cases carbon ends up with 8 electrons in its valence shell.