Are two atoms of the same element identical?

Which of the following statements is true? a. elements in the last period are radioactive. b. atomic weight is the same as atomic mass. c. elements in the same group have the same number of electron shells. d. atomic number equals the number of neutrons in the nucleus of an atom.

What best discribes the relationship between wavelength and frequency in a electromagnetic wave

How does a large body of water, such as the ocean, influence climate?