The atomic number Z refers to what?

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Multiple Choice

The atomic number Z refers to what?

The atomic number Z is the number of protons in the nucleus, and that count uniquely identifies the element. Neutrons add to the mass, giving the mass number A (A = protons + neutrons), so A can vary with isotopes while Z stays the same. The number of electrons can differ with ionization, and the total charge depends on the balance of protons and electrons, but Z itself does not refer to electrons or to the overall charge. So, Z specifically counts the protons in the nucleus, defining the element.

The atomic number Z is the number of protons in the nucleus, and that count uniquely identifies the element. Neutrons add to the mass, giving the mass number A (A = protons + neutrons), so A can vary with isotopes while Z stays the same. The number of electrons can differ with ionization, and the total charge depends on the balance of protons and electrons, but Z itself does not refer to electrons or to the overall charge. So, Z specifically counts the protons in the nucleus, defining the element.

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