Question

an atom of iron has an atomic number of 26. which of the following is true?
a iron has 13 protons and 13 neutrons
b iron has 13 protons and 13 electrons
c iron has 13 electrons
d iron has 26 protons

Explanation:

The atomic number of an element is equal to the number of protons in its atom. Since iron has an atomic number of 26, it must have 26 protons. In a neutral atom (which is the default assumption unless stated otherwise), the number of electrons equals the number of protons. So iron also has 26 electrons. We don't have information about the number of neutrons from just the atomic number (mass number is needed for that, calculated as protons + neutrons).

• Option A: Incorrect. Atomic number = 26 ≠ 13 (protons).
• Option B: Incorrect. Atomic number = 26 ≠ 13 (protons).
• Option C: Incorrect. Should be 26 electrons (if neutral).
• Option D: Correct. Atomic number = number of protons = 26.

Answer:

D. iron has 26 protons