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The graph shows the radioactive decay of a bone that is found to contain 1/8 of the carbon-14 found in living animals today.

Approximately how old is the bone?

a
22,920 years
b
5,730 years
c
11,460 years
d
17,190 years

11 answers

Carbon-14 has a half-life of approximately 5,730 years. To determine the age of the bone, we need to find out how many half-lives it has gone through to reach 1/8 of the original amount.

  1. Each half-life reduces the amount of Carbon-14 by half:
    • After 1 half-life: 1/2
    • After 2 half-lives: 1/4
    • After 3 half-lives: 1/8

Since the bone contains 1/8 of the original Carbon-14, it has gone through 3 half-lives.

Calculating the total age:

  • 3 half-lives × 5,730 years/half-life = 17,190 years

Therefore, the approximate age of the bone is 17,190 years (d).

9 0

BE

4

In the element above the mass number is and the atomic number is .

In the notation you've provided, it seems like you're referring to a chemical element where:

  • The number above (9) indicates the mass number, which is the total number of protons and neutrons in the nucleus.
  • The number below (4) indicates the atomic number, which is the number of protons in the nucleus and also identifies the element.

From this information, we can determine that:

  • The mass number is 9.
  • The atomic number is 4.

The atomic number of 4 corresponds to the element Beryllium (Be).

So to summarize:

  • Mass number = 9
  • Atomic number = 4
Why does the chloride ion have a -1 charge?

a
Chlorine atoms gain an electron.
b
Chlorine atoms lose an electron.
c
Chlorine atoms have no electrons.
d
Chlorine atoms share electrons.

The chloride ion (Cl⁻) has a -1 charge because:

a. Chlorine atoms gain an electron.

When a chlorine atom gains one electron, it has one more electron than protons, resulting in a net charge of -1. This is the reason why the chloride ion has a negative charge.

Technetium-99m is a radioactive isotope commonly used in medicine as a radioactive tracer. A radioactive tracer is an isotope injected into the body to help create images for diagnosis of health problems. Technetium-99m has a half-life of 6 hours. If a patient receives a dose of technetium-99m one morning, about what percentage of the technetium-99m will be left in the patient's body 12 hours later?

a
12.5%
b
93.8%
c
25.0%
d
6.25%

To determine the percentage of technetium-99m left in the patient's body after 12 hours, we can use the half-life information.

Technetium-99m has a half-life of 6 hours. Therefore, in 12 hours, the technetium-99m will undergo 2 half-lives (since \(12 , \text{hours} \div 6 , \text{hours/half-life} = 2\)).

We can calculate the remaining quantity after each half-life:

  1. After 1 half-life (6 hours):

    • 50% remains.

  2. After 2 half-lives (12 hours):

    • 50% of the remaining 50%: \(50% \times 0.5 = 25%\).

So, after 12 hours, approximately 25.0% of the technetium-99m will be left in the patient's body.

The correct answer is c. 25.0%.

Compared to an ordinary chemical reaction, a fission reaction will:

a
release a smaller amount of energy.
b
absorb a smaller amount of energy.
c
absorb a larger amount of energy.
d
release a larger amount of energy.

Compared to an ordinary chemical reaction, a fission reaction will:

d. release a larger amount of energy.

Nuclear fission involves the splitting of atomic nuclei (such as those of uranium or plutonium), which releases a significant amount of energy due to the strong nuclear forces that hold the nucleus together. This energy release is much greater than what is typically observed in ordinary chemical reactions, which involve the rearrangement of electrons and chemical bonds.

Nuclear reactions always involve lots of energy.

True
False

True.

Nuclear reactions involve changes in the nucleus of an atom, such as fission (splitting of atoms) or fusion (combining of atoms), resulting in the release or absorption of a significant amount of energy. This energy is much larger when compared to chemical reactions, which primarily involve electron interactions. Thus, it's accurate to say that nuclear reactions always involve lots of energy.