Question

An atom of sodium has an atomic number of 11 and a mass number of 23. Which of the following statements is correct?

• A. An atom of sodium has 11 protons, 11 electrons, and 11 neutrons.
• B. An atom of sodium has 11 protons, 12 electrons, and 11 neutrons.
• C. An atom of sodium has 11 protons, 11 electrons, and 12 neutrons.
• D. An atom of sodium has 11 protons, 12 electrons, and 12 neutrons

Answer 1

The correct option is C

An atom of sodium has 11 protons, 11 electrons, and 12 neutrons.

An atom is an uncharged species .It must therefore comprise an equal number of protons and electrons .This number is denoted by atomic number ,by contrast , the mass number tells us the sum of the number of protons and number of neutrons in an atom of a given element.The number of neutrons may not be the same as the number of protons or electrons.