CHE 105/110 Introduction to Chemistry - Exercises and Answers

1.

List the three statements that make up the modern atomic theory.

1.

All matter is composed of atoms; atoms of the same element are the same, and atoms of different elements are different; atoms combine in whole-number ratios to form compounds.

3.

Which is larger, a proton or an electron?

3.

A proton is larger than an electron.

5.

What are the charges for each of the three subatomic particles?

5.

proton: 1+; electron: 1−; neutron: 0

7.

Sketch a diagram of a boron atom, which has five protons and six neutrons in its nucleus.

7.

9.

Define atomic number. What is the atomic number for a boron atom?

9.

The atomic number is the number of protons in a nucleus. Boron has an atomic number of five.

11.

Define isotope and give an example.

11.

Isotopes are atoms of the same element but with different numbers of neutrons. $\text{1}\text{1}\text{H}$ and $\text{2}\text{1}\text{H}$ are examples.

13.

Which pair represents isotopes?

2. ${}_{26}{}^{56}\text{F}\text{e}$ and ${}_{25}{}^{56}\text{M}\text{n}$


3. ${}_{14}{}^{28}\text{S}\text{i}$ and ${}_{15}{}^{31}\text{P}$

13.

1. isotopes
2. not isotopes
3. not isotopes

15.

15

1. ${}_8{}^{16}\text{O}$


2. ${}_{19}{}^{39}\text{K}$


3. ${}_3{}^7\text{L}\text{i}$

17.

Americium-241 is an isotope used in smoke detectors. What is the complete symbol for this isotope?

17.

${}_{95}{}^{241}\text{A}\text{m}$

19.

19.

1. Na
2. Ar
3. N
4. Rn

21.

21.

1. silicon
2. manganese
3. iron
4. chromium