Question

1. what is an isotope?
2. what does the number next to isotopes signify?
3. how can you tell isotopes apart?

Explanation:

1. What is an isotope?

Isotopes are atoms of the same element (same atomic number, i.e., same number of protons) that have different numbers of neutrons, resulting in different mass numbers. For example, carbon - 12, carbon - 13, and carbon - 14 are isotopes of carbon. Carbon - 12 has 6 protons and 6 neutrons, carbon - 13 has 6 protons and 7 neutrons, and carbon - 14 has 6 protons and 8 neutrons.

The number next to an isotope (e.g., in carbon - 14) is the mass number. The mass number is the sum of the number of protons and neutrons in the nucleus of an atom. For an isotope, since the number of protons (atomic number) is fixed for a given element, the mass number is determined by the sum of protons and neutrons, and different isotopes of the same element have different mass numbers because of different numbers of neutrons.

To tell isotopes apart, we can look at their mass numbers (or the number of neutrons) since they have the same number of protons (same atomic number, so same element). We can also distinguish them by their physical properties (like atomic mass, due to different numbers of neutrons) or their radioactive properties (if they are radioactive isotopes, like carbon - 14 is radioactive while carbon - 12 is not).

Answer:

Isotopes are atoms of the same element with the same number of protons (same atomic number) but different numbers of neutrons (different mass numbers).

2. What does the number next to isotopes signify?