1. A B 21085At-1 5526Fe3+ 9642Mo 5827Co 3216S2- 20782Pb4+ Symbol
Symbol
Atomic Mass
Atomic number
Protons
Neutrons
Electrons A
 21085At-1
5526Fe3+
9642Mo B
5827Co
3216S2-
20782Pb4+

2. Naturally occurring magnesium consists of three stable isotopes: 24 Mg, amu (78.99%); 25 Mg, amu (10.00%); and
26 Mg, amu (11.01%).
Calculate the average atomic mass of magnesium.   
B amu is the mass of 60.4% of the atoms of an element with only two naturally occurring isotopes. The atomic mass of the other isotope is amu. Determine the average atomic mass of the element.

3. A B Symbol Atomic Mass Atomic number Protons Neutrons Electrons
Symbol
Atomic Mass
Atomic number
Protons
Neutrons
Electrons A
21085At-1
210 85
125 86
5526Fe3+ 55 26 29 23
9642Mo 96 42 54 B
5827Co 58 27 31
3216S2- 32 16 18
20782Pb4+
207 82 78

4. A amu (0.7899) = 18.95
amu (0.1000) =
amu (0.1101) = Mg amu   
B amu (0.604) = 41.6
amu (0.396) = 28.1
Ga 69.7 amu