PRACTICE

Determine the number of protons, electrons and neutrons in the different examples:

1.  197 Au, the atomic number is 97. p= 97, e= 97, n=100

2.  39 K, the atomic number is 19. p=19, e=19, n=20

3.  Se -2, it has 34 protons. P=34, e=36, n=34

4.  An atom’s nucleus has 28 protons and a mass number of 60. n= 32, p=28, e=28

5.  Here are three isotopes of an element: 612C 613C 614C

a.  The element is: ______carbon______

b.  The number 6 refers to the ____atomic number______

c.  The numbers 12, 13, and 14 refer to the mass number_

d.  How many protons and neutrons are in the first isotope? ______p=6, n=6______

e.  How many protons and neutrons are in the second isotope? _p=6, n=7______

f.  How many protons and neutrons are in the third isotope? ______p=6, n=8______

6. Complete the following chart:

Isotope name / atomic # / mass # / # of protons / # of neutrons / # of electrons
92 uranium-235 / 92 / 235 / 92 / 143 / 92
92 uranium-238 / 92 / 238 / 92 / 146 / 92
5 boron-10 / 5 / 10 / 5 / 5 / 5
5 boron-11 / 5 / 11 / 5 / 6 / 5

7. 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?

152 amu

8. 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. 87.70amu

9. Explain how atoms of U-235 and U-238 are similar and how they differ. Both are isotopes of Uranium, have the same atomic number, but different mass number, that means different number of neutrons.

10. Rubidium is a soft, silvery-white metal that has two common isotopes, 85Rb and 87Rb. If the abundance of 85Rb is 72.2% and the abundance of 87Rb is 27.8%, what is the average atomic mass of rubidium? 85.56amu

11. Uranium is used in nuclear reactors and is a rare element on earth. Uranium has three common isotopes. If the abundance of 234U is 0.01%, the abundance of 235U is 0.71%, and the abundance of 238U is 99.28%, what is the average atomic mass of uranium? 237.98amu

12. Titanium has five common isotopes: 46Ti (8.0%), 47Ti (7.8%), 48Ti (73.4%),

49Ti (5.5%), 50 Ti (5.3%). What is the average atomic mass of titanium? 47.92 amu