The vertical columns on the periodic table are called groups or families because of their similar chemical behavior. All the members of a family of elements have the same number of valence electrons and similar chemical properties. The horizontal rows on the periodic table are called periods.
According to the reaction equation:
Ba(OH)2 ↔ Ba2+ + 2OH-
when 0.015 M 0.015M 2*0.015M
∴ [OH-] = 0.03 m
so we can get the POH = - ㏒ [OH-]
by substitution:
∴ POH = -㏒ 0.03
= 1.52
and then we can get the PH from this formula:
PH + POH = 14
so by substitution:
∴PH = 14 - 1.52
≈ 12.48
12
Neon is the 10th element and has 10 protons. The mass of an element is the sum of the protons and neutrons.
22-10=12