Question

1. four isotopes of lead include lead - 204, lead - 206, lead - 207, and lead - 208. the average atomic mass of a lead atom is 207.2 amu. which isotope of lead is likely to be the most abundant?
2. what do all isotopes of an element have in common?
3. explain why carbon - 14 and nitrogen - 14 are not considered isotopes.

Explanation:

1. The average atomic mass is closest to the mass of lead - 207 and 208. Since the average is a weighted - average based on the abundance of isotopes, the isotopes with masses closest to the average atomic mass are likely to be the most abundant. So lead - 207 and lead - 208 are likely the most abundant.
2. All isotopes of an element have the same number of protons. This is what defines an element. The number of neutrons can vary among isotopes, but the proton number (atomic number) remains constant.
3. Isotopes are atoms of the same element with different numbers of neutrons. Carbon - 14 is an atom of carbon and nitrogen - 14 is an atom of nitrogen. Since they are atoms of different elements (carbon has 6 protons and nitrogen has 7 protons), they are not isotopes.

Answer:

1. Lead - 207 and lead - 208 are likely the most abundant.
2. The same number of protons.
3. They are atoms of different elements (carbon has 6 protons and nitrogen has 7 protons).