Which is the best definition of force?
A. a push or pull
B. a change in motion
C. a motion that does not change

A

Explanation:

push or pull i think..okay?

n has four pairs of electrons in the valence shell, electrons repel one another ,n has 7 protons in its nucleus, and since n has 7 protons, it must fill the second shell, giving it 4 pairs of electrons. the electrons form 3 bonds and 1 lone pair of electrons. each pair of electrons repels the other pairs, so they are equally far apart.

so all of the above

it's c. elements are placed in rows based on how may valencies electrons have.