Atoms of elements in a group on the Periodic Table have similar chemical properties. This similarity is most closely related to the atoms:
A. atomic masses.
B. atomic numbers.
C. number of valence electrons.
D. number of principal energy levels.
E. All of the above.
Most of the time elements in the same group have the same number of valence electrons. Valence electrons are involved in bonding and this effects how elements react and determines their chemical properties.