Question

question 13 (5 points)
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which of the following best describes an atomic number? an elements identity is defined by its atomic number; this means it represents the number of
a) protons in its nucleus.
b) protons plus neutrons in its nucleus.
c) electrons in the element.
d) neutrons in its nucleus.

Explanation:

To determine the correct answer, we recall the definition of atomic number. The atomic number of an element is defined as the number of protons in the nucleus of an atom of that element. This number determines the element's identity.

• Option B: Protons plus neutrons is the mass number, not the atomic number.
• Option C: The number of electrons can change (e.g., in ions), so it does not define the element's identity.
• Option D: Neutrons can vary (isotopes), so they do not define the element's identity.
• Option A: The number of protons in the nucleus is the atomic number and defines the element.

Answer:

A) protons in its nucleus.