Name _____________________________________ Class _____________ Date ________________
Isotopes
Isotopes are atoms of same element with different number of neutrons.
General Abbreviation:
atomic mass
X = symbol of an element
atomic number
Atomic mass = protons + neutrons
Neutrons = atomic mass – atomic number
In a neutral atom Atomic number = # of protons = # of electrons
The following are three isotopes of an element:
1. The element is: __________________
2. The number 1 refers to the _________________________
3. The numbers 1, 2, and 3 refer to the ________________________
4. How many protons and neutrons are in the first isotope? _________________
5. How many protons and neutrons are in the second isotope? _________________
6. How many protons and neutrons are in the third isotope? _________________
Complete the following chart:
Nuclear
Name of
Symbol
element
7.
Atomic
number
Protons
Neutrons
8
9
8.
77
Electrons
54
9.
10.
38
50
11
12
47
61
11.
12.
13.
14.
11
Atomic
Mass
15.
16. Naturally occurring europium (Eu) consists of two isotopes was a mass of 151 and 153. Europium-151
has an abundance of 48.03% and Europium-153 has an abundance of 51.97%. What is the atomic mass of
europium?
17. Strontium consists of four isotopes with masses of 84 (abundance 0.50%), 86 (abundance of 9.9%), 87
(abundance of 7.0%), and 88 (abundance of 82.6%). Calculate the atomic mass of strontium.
18. The element copper has naturally occurring isotopes with mass numbers of 63 and 65.
The relative abundance and atomic masses are 69.2% for a mass of 62.93amu and 30.8% for a mass of
64.93amu. Calculate the average atomic mass of copper.