How many protons, neutrons and electrons are there altogether in an ammonium ion with a relative formula mass of $21$?
- Anumber of protons: $11$, number of neutrons: $10$, number of electrons: $10$
- Bnumber of protons: $10$, number of neutrons: $11$, number of electrons: $11$
- Cnumber of protons: $10$, number of neutrons: $11$, number of electrons: $10$
- Dnumber of protons: $11$, number of neutrons: $10$, number of electrons: $11$