The mass number for an atom is numerically equal to which
quantity?

Uranium has the atomic number 92; its atoms contain 92 protons and 92 electrons. Each atom also has a mass number, denoted by the symbol A. The mass number of an atom is equal to the number of protons plus the number of neutrons that it contains.

Explanation:

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1. a)c-14 has two more protons

2. d)they have different numbers of protons, neutrons, and valence electrons; they are all gases at room temperature.

3. c) iron and nickel.