Principal: Mr. T. Power, B.A. H.D.E.
Vice Principal: Ms. F. Greene, B.A. H.D.E.

Junior Cert

SCIENCE > ATOMIC STRUCTURE

1. Atomic Number
The atomic number tells us three things:
(a) the number of electrons
(b) the number of protons
(c) the position of the element on the periodic table.

Note: the atomic number is the small number.

2. Mass number
The mass number is the number of protons plus neutrons in an atom.

Note: the mass number is the big number.