An element X has a mass number of 40 and 21 neutrons. The number of electrons in the X²⁺ ion is
A21
B19
C17CORRECT
D22
GCEChemistryAtomic Structure and Periodicity2024
AI
Toaster Teacher
Why the answer is C, and why the others tempt you.
The atomic number (protons) = mass number − neutrons = 40 − 21 = 19, so the neutral atom has 19 electrons. The X²⁺ ion has lost 2 electrons, leaving 19 − 2 = 17 electrons.
Want this in Pidgin, Yoruba, Igbo or Hausa? Sign up free →
Practice more Chemistry questions
GCE Chemistry has thousands more questions like this — with Worked answers on every one.