5. Subatomic
particles
Charge
Mass (g) ~size (m)
Coulumb Charge unit
electron -1.6022 x 10-19 -1 9.10939 x 10-28
Not known
exactly
(~1 x 10-18)
proton +1.6022 x 10-19 +1 1.67262 x 10-24 1 x 10-15
neutron 0 0 1.67493 x 10-24 1 x 10-15
6. • Elements differ in the number of protons, electrons, and neutrons.
• Identity of an element is based on the number of protons equates to the
atomic number.
EXAMPLE:
Atomic number = number of
protons
For neutral atom:
Number of protons = number of electrons
Number of electrons = 11
7. Elements are generally represented by a nuclide symbol:
• Mass number = number of protons + number of neutrons
• Number of neutrons = mass number – atomic number
N = A - Z
8. What is the difference between mass number and atomic number?
ELEMENTS
Na K Mg Al N
Mass number 23 24 14
Atomic Mass
Identify the atomic mass and mass number of the following elements:
9. ELEMENTS
Na K Mg Al N
Mass number 23 39 24 27 14
Atomic Mass 22.9898 39.0983 24.305 26.9815 14.0067
