1. ATOMIC STRUCTURE THE NUCLEUS: 1) THE PROTON:
A) WEIGH 1 AMU ( 1/12 THE MASS OF COLD CARBON, 12C ).
B) CONTRIBUTES MASS TO THE ATOM.
C) THE NUMBER OF PROTONS IS INDICATED BY THE ATOMIC MASS NUMBER
a) THE PROTON HAS A POSITIVE CHARGE
b) INDICATES NUCLEAR CHARGE.
c) INDICATES NUMBER OF ELECTRONS IN A NEUTRAL ATOM.
d) INDICATES WHAT ELEMENT THE PARTICLE IS.
e) SPECIFIC ELEMENTS HAVE SPECIFIC ATOMIC NUMBERS( EX CARBON HAS AN ATOMIC NUMBER OF 6, 6 PROTONS, ONY CARBON HAS SIX PROTONS).
2) THE NEUTRON:
A) WEIGH 1 AMU.
B) CONTRIBUTES THE BALANCE OF MASS TO THE ATOM (THE REST IS PROTONS).
C) REDUCES PROTON REPULSION.
D) HAS NO CHARGE.
E) THE NUMBER OF NEUTRONS CAN CHANGE BETWEEN ATOMS.
F) IF TWO PARTICLES DIFFER IN THE NUMBER OF NEUTRONS RTHEY ARE CALLED ISOTOPES.

3. Calculate the average atomic weight for:
1) magnesium
mass number exact weight percent abundance

4. This is the solution for carbon:
Problem #1: Carbon
To calculate the average atomic
mass number
exact weight
percent abundance 12
98.90 13
1.10
To calculate the average atomic weight, each exact atomic weight is multiplied by its percent abundance (expressed as a decimal). Then, add the results together and round off to an appropriate number of significant figures.
This is the solution for carbon:
( ) (0.9890) + ( ) (0.0110) = amu
ANOTHER EXAMPLE