Final answer:
The number of neutrons for the isotopes are: helium-3 has 1 neutron, carbon-14 has 8 neutrons, nitrogen-15 has 8 neutrons, strontium-90 has 52 neutrons, and tellurium-123 has 71 neutrons. These figures are determined by subtracting the atomic number (Z) from the mass number (A) of each isotope.
Step-by-step explanation:
To determine the number of neutrons in the given isotopes, we use the formula N = A - Z, where N is the number of neutrons, A is the mass number (total number of protons and neutrons), and Z is the atomic number (number of protons). For each isotope, the mass number is the larger number in the isotope's name (e.g., carbon-14), and the atomic number can be found on the periodic table based on the element's symbol.
- Helium-3 (He-3): A = 3, Z = 2 (Helium), N = 3 - 2 = 1 neutron.
- Carbon-14 (C-14): A = 14, Z = 6 (Carbon), N = 14 - 6 = 8 neutrons.
- Nitrogen-15 (N-15): A = 15, Z = 7 (Nitrogen), N = 15 - 7 = 8 neutrons.
- Strontium-90 (Sr-90): A = 90, Z = 38 (Strontium), N = 90 - 38 = 52 neutrons.
- Tellurium-123 (Te-123): A = 123, Z = 52 (Tellurium), N = 123 - 52 = 71 neutrons.
Remember, the atomic number corresponds to the number of protons in an element's nucleus, which is consistent across all isotopes of that element.