A: Helium atoms have just two protons, two neutrons, and two electrons, so they have less mass than any other atoms except hydrogen. As a result, helium is lighter than air, explaining why a helium balloon floats up into the air unless weighted down.

Keep this in mind about the number of valence electrons and the Roman numeral column number: The IA family has 1 valence electron; the IIA family has 2 valence electrons; the VIIA family has 7 valence electrons; and the VIIIA family has 8 valence electrons.

Carbon Group or Tetrels: – Group 14 (IVA) – 4 valence electrons.

arsenic

Aluminum atoms contain 13 electrons and 13 protons. There are 3 valence electrons in the outer shell. In standard conditions aluminum is a fairly soft, strong, and lightweight metal. Its color is silvery-gray.

The third period contains only eight elements even though the electron capacity of the third shell is 18 because when the other shells get filled and the resultant number of electrons becomes eighteen, it gets added up and settles in the third electron shell and three shells are acquired by the fourth period.

Biological role. Many period 4 elements find roles in controlling protein function as secondary messengers, structural components, or enzyme cofactors. A gradient of potassium is used by cells to maintain a membrane potential which enables neurotransmitter firing and facilitated diffusion among other processes.

For Period 3, the Group1 Alkali Metal (potassium, lowest Z) has the largest atomic radius and the Group 7/17 Halogens & Group 0/18 Noble Gas (bromine & krypton, highest Z’s) have the smallest atomic radii (there is some uncertainty in the noble gas radii)….