Question

How many total electrons are in a $B{{a}^{2+}}$ ions?

Answer 1

Hint:We should know the atomic number of the Barium atom and then calculate the number of protons and electrons from the atomic number. Then consider the magnitude and sign of the charge present in the species.

Complete step-by-step answer:So in the question, it is asked that we have to calculate the number of protons present in the species given. First to calculate the number of protons or electrons present in the given species, we should have a brief idea about atomic structure, atomic number and mass number. And how they are related to the number of electrons, protons or neutrons present in an atom and how they account for the stability of an atom.
An atom consists of a massive nucleus in which the positively charged species called as the protons are present and it has +1 charge and has mass. Along with protons, neutrons are also present in the nucleus and they are neutral species i.e. they do not possess any charge and have only mass. These two species which are called as the nucleons is the reason for the mass of the nucleus and the mass of the nucleus is considered as the mass number.
The electrons are distributed around the nucleus in order to maintain the stability of the atom. The number of electrons or number of protons present will be equal to the atomic number of the atom.
 Hence if we know the atomic number of Ba atom, then we could calculate the number of electrons of the neutral Ba atom.
The atomic number of Ba is 56, i.e. a neutral Ba atom has 56 electrons.
But here a charged species of Ba is given a divalent ion is given with positive charge, an atom loses one electron to gain one positive charge. So here, from the atom two electrons are lost to gain +2 charge and form $B{{a}^{2+}}$.
$Ba\to B{{a}^{2+}}+2{{e}^{-}}$
$No.\,of\,electrons=56-2=54$
Therefore there are in total 54 electrons in $B{{a}^{2+}}$.

Note:If a negatively charged species is given then we have to add electrons given accordingly to the atomic number to obtain the number of electrons for the given negatively charged species. For a charged species only the electrons varies; the number of protons remains the same as the atomic number.