If the following element undergoes alpha decay, which element does it change into?

Question

234/90 TH

a
Uranium (U)
b
Francium (Fr)
c
Radium (Ra)
d
Radon (Rn)

A stable nucleus will decay, or emit, particles.

True
False

The amount of time it takes for half of a sample to disappear is:

a
half-life
b
fission
c
fusion
d
nuclear chemistry

The half-life for a 100-gram sample of radioactive element X is 5 days. How much of element X remains after 10 days have passed?

a
25 g
b
50 g
c
75 g
d
100 g

Sodium-24 has a half-life of approximately 15 hours. If only one-eighth of the sodium-24 remains, about how much time has passed?

a
30 hours
b
45 hours
c
60 hours
d
15 hours

Answer 1

1. If the element \( \frac{234}{90} \text{Th} \) (Thorium) undergoes alpha decay, it loses 2 protons and 2 neutrons, transforming into \( \frac{230}{88} \text{Ra} \) (Radium). Thus, the answer is c) Radium (Ra).

2. A stable nucleus will decay, or emit, particles.
   False. (Only unstable nuclei decay.)

3. The amount of time it takes for half of a sample to disappear is:
   a) half-life.

4. The half-life for a 100-gram sample of radioactive element X is 5 days. After 10 days, which is two half-lives, the amount remaining can be calculated as follows:

   • After 5 days (1 half-life): 100 g → 50 g
   • After another 5 days (2 half-lives): 50 g → 25 g Therefore, the answer is a) 25 g.

5. Sodium-24 has a half-life of approximately 15 hours. If only one-eighth of the sodium-24 remains, this means that three half-lives have passed (since \( \frac{1}{2^3} = \frac{1}{8} \)). Therefore:

   • 15 hours per half-life × 3 half-lives = 45 hours. Thus, the answer is b) 45 hours.

Answer 2

Match the particle to its description.

Column A

Relatively large particle

This particle cannot penetrate very far into other materials

Can be absorbed by a sheet of paper

Can penetrate other materials moderately

Can be absorbed by a sheet of aluminum

Has no mass and a negative charge

Has no mass and no charge

Can be absorbed by lead

Can travel long distances

Column B

alpha particle

gamma particle

beta particle

Answer 3

Here’s how the particles from Column A match with their descriptions in Column B:

1. Relatively large particle

   • Match: alpha particle

2. This particle cannot penetrate very far into other materials

   • Match: alpha particle

3. Can be absorbed by a sheet of paper

   • Match: alpha particle

4. Can penetrate other materials moderately

   • Match: beta particle

5. Can be absorbed by a sheet of aluminum

   • Match: beta particle

6. Has no mass and a negative charge

   • Match: beta particle

7. Has no mass and no charge

   • Match: gamma particle

8. Can be absorbed by lead

   • Match: gamma particle

9. Can travel long distances

   • Match: gamma particle

Summary of Matches:

• alpha particle: Relatively large particle, cannot penetrate very far into other materials, can be absorbed by a sheet of paper.
• beta particle: Can penetrate other materials moderately, can be absorbed by a sheet of aluminum, has no mass and a negative charge.
• gamma particle: Has no mass and no charge, can be absorbed by lead, can travel long distances.

Answer 4

Match the part of an atom to its description.

Column A

proton

neutron

electron

nucleus

electron cloud

Column B
a.negatively charged particle
b.the area of the atom where positive particles and neutral particles are found
c.the area of the atom where negatively charged particles are found
d.neutral particle
e.positively charged particle

Answer 5

Here is how the parts of an atom from Column A match with their descriptions in Column B:

1. proton

   • Match: e. positively charged particle

2. neutron

   • Match: d. neutral particle

3. electron

   • Match: a. negatively charged particle

4. nucleus

   • Match: b. the area of the atom where positive particles and neutral particles are found

5. electron cloud

   • Match: c. the area of the atom where negatively charged particles are found

Summary of Matches:

• proton: e. positively charged particle
• neutron: d. neutral particle
• electron: a. negatively charged particle
• nucleus: b. the area of the atom where positive particles and neutral particles are found
• electron cloud: c. the area of the atom where negatively charged particles are found

Answer 6

Match the group to the type of ions they form

Column A

group 1A

group 2A

group 3A

group 4A

group 5A

group 6A

group 7A

group 8A


Column B
a.+3
b.+1
c.+4/-4
d.0
e.+2
f.-1
g.-2
h.-3

Answer 7

Here’s how the groups from Column A match with the types of ions they form in Column B:

1. group 1A

   • Match: b. +1

2. group 2A

   • Match: e. +2

3. group 3A

   • Match: a. +3

4. group 4A

   • Match: c. +4/-4 (Group 4A can form +4 cations or -4 anions, as seen with lead and tin or carbon and silicon respectively)

5. group 5A

   • Match: h. -3 (Nonmetals in this group, like nitrogen and phosphorus, typically gain 3 electrons to form -3 anions)

6. group 6A

   • Match: g. -2 (Group 6A nonmetals like oxygen and sulfur typically gain 2 electrons to form -2 anions)

7. group 7A

   • Match: f. -1 (Group 7A halogens typically gain 1 electron to form -1 anions)

8. group 8A

   • Match: d. 0 (Noble gases are generally unreactive and do not typically form ions, hence a charge of 0)

Summary of Matches:

• group 1A: b. +1
• group 2A: e. +2
• group 3A: a. +3
• group 4A: c. +4/-4
• group 5A: h. -3
• group 6A: g. -2
• group 7A: f. -1
• group 8A: d. 0

Answer 8

Question 19
What happens to the volume of a gas when the temperature is increased?

a
The volume is increased
b
The volume stays the same
c
The volume is decreased

Question 20
Which of the following will increase the rate at which a solute dissolves? (Select all that apply.)

a
increasing temperature
b
stirring
c
increasing surface area
d
decreasing temperature
e
decreasing surface area

Match the pH to its description.

Column A

pH above 7

pH below 7

pH of 7

Column B
a.acidic
b.basic
c.neutral

Answer 9

Question 19

What happens to the volume of a gas when the temperature is increased?

• Answer: a. The volume is increased (according to Charles's Law, which states that at constant pressure, the volume of a gas is directly proportional to its absolute temperature).

Question 20

Which of the following will increase the rate at which a solute dissolves? (Select all that apply.)

• Answers:

  • a. increasing temperature
  • b. stirring
  • c. increasing surface area

  (Decreasing temperature and decreasing surface area would slow down the rate at which a solute dissolves.)

Match the pH to its description.

1. pH above 7

   • Match: b. basic

2. pH below 7

   • Match: a. acidic

3. pH of 7

   • Match: c. neutral

Summary

• Volume of gas when temperature increases: a. The volume is increased
• Rate of solute dissolving: a. increasing temperature, b. stirring, c. increasing surface area
• pH Matches:
  • pH above 7: b. basic
  • pH below 7: a. acidic
  • pH of 7: c. neutral