Question

How do electron configurations affect properties and trends of a compound?

Answer 1

The most important consequence of electron configurations is the number of bonds that an atom can form to other atoms.

Example:
An oxygen atom has a `2p^4` configuration in the valence shell, which means that two electrons are unpaired, and it can form bonds to two other atoms (e.g., `H_2O`) or two bonds to one other atom (e.g., `O_2`).

Carbon has a `2s^2 2p^2` electron configuration (2 unpaired electrons), and in this configuration it can bind to two other atoms (e.g., `CH_2` radical). But another low-energy configuration, `2s^1 2p^3`, has 4 unpaired electrons and can bind to 4 other atoms (e.g., `CH_4`). which is usually much more energetically favorable.

There are other consequences of electron configurations that lead to specific spectroscopic and magnetic properties, but bonding is the most important.