Question

1. what is the difference between the compositions of these carbon isotopes?

	protons	electrons	neutrons
carbon - 13
carbon - 14

1. what happens to carbon - 14 over time?
2. define radioactive half - life:
3. based on carbon dating, how long ago did the tree die?

Explanation:

Step1: Recall properties of isotopes

Isotopes of an element have the same number of protons and electrons, but different numbers of neutrons. Carbon has atomic number 6. So for all carbon isotopes, number of protons = 6 and number of electrons = 6.
Number of neutrons for Carbon - 12: $12 - 6=6$.
Number of neutrons for Carbon - 13: $13 - 6 = 7$.
Number of neutrons for Carbon - 14: $14 - 6=8$.

	Protons	Electrons	Neutrons
Carbon - 13	6	6	7
Carbon - 14	6	6	8

Step2: Answer question 20

Carbon - 14 is a radioactive isotope. Over time, it undergoes radioactive decay. It decays into nitrogen - 14 by emitting a beta particle.

Step3: Define radioactive half - life

Radioactive half - life is the time required for half of the atoms of a radioactive substance to decay.

Step4: Regarding question 22

No data about the carbon - dating results of the tree is provided, so we cannot calculate how long ago the tree died.

Answer:

19.

	Protons	Electrons	Neutrons
Carbon - 13	6	6	7
Carbon - 14	6	6	8

1. Carbon - 14 undergoes radioactive decay into nitrogen - 14 by emitting a beta particle.
2. The time required for half of the atoms of a radioactive substance to decay.
3. Insufficient data to answer.