Name:_____________
Period:________
Sections 2.1 – 2.4 Overview
1. Who are the people that helped lay the foundation for atomic theory, and how did each person contribute
to the atomic theory?
2. What are the postulates for Dalton’s atomic theory?
3. What does the law of constant composition state? Law of conservation of mass? Law of multiple
proportions?
4. What are the subatomic particles and who is credited with discovering them?
5. Who “discovered” electrons and what were they initially called?
6. Robert Millikan performed what experiment? What did he measure in this experiment? What was he
able to calculate from this experiment?
.
7. Who were the scientists that were instrumental in discovering radioactivity? What are the three types of
radiation and give the properties of these types?
8. Who discovered that the atom has nucleus and is made up of mostly empty space? Describe the
experiment that allowed him to discover the nucleus. What subatomic particle did he discover eight
years later?
9. Who discovered neutrons?
10. Which occupies the majority of the space of an atom, an electron or the nucleus?
11. What is the common unit of measure for the mass of a single atom? Length?
12. The diameter of a U.S. quarter is 24 mm. The diameter of a gold atom, by comparison, is only 14.88 Å.
How many gold atoms could be arranged side by side in a straight line across the diameter of a quarter?
Hint: see sample exercise 2.1
13. What is the atomic number? Mass number? Give an example of element using its symbol and identify
its mass number and atomic number.
14. Determine the number of protons, neutrons, and electrons in the following atoms
a. 197Au
b. Strontium-89
c. Phosphorus-30
d.
137
Ba
15. What are isotopes? Give examples of isotopes.
.
16. What are atomic weights measured in? What does the average atomic weight account for?
17. Naturally occurring chlorine is 75.78% 35Cl, which has an atomic mass of 34.969 amu, and 24.22% 37Cl,
which has atomic mass of 36.966 amu. Calculate the average atomic mass (that is, the atomic weight) of
chlorine.
18. Three isotopes of silicon occur in nature: 28Si (92.23%), which has an atomic mass of 27.97693 amu;
29
Si (4.68%), which has an atomic mass of 28.97649 amu; and 30Si (3.09%), which has an atomic mass
of 29.97377 amu. Calculate the atomic weight of silicon.