Question

Give the number of electrons in the species $H_2^ + $, ${H_2}$ and $O_2^ + $.

Answer 1

Hint: The number of electrons in an atom is always equal to the atomic number of an element. If there is a positive charge on a species, then that number is to be subtracted from the given number of electrons and if there is negative charge then, this number is to be added. This way, we can find the number of electrons.

Complete step by step answer:
Let us see how the number of electrons vary from species to species and how we can calculate them
-The electron can be defined as the subatomic particle which has negative charge.
-The number of electrons in an atom is always equal to the number of protons or atomic number. Further, if the species contain a positive charge, then this must be subtracted from the atomic number and in case the charge is negative, then this must be added to the atomic number.
-Now, let us see the molecules one by one.
-The first molecule given is $H_2^ + $. The atomic number for H is 1. Thus, one atom will contain one electron. As there are two atoms, so two electrons. There is one positive charge. So, subtracting 1, we have 1 electron.
-The second molecule is ${H_2}$. The atomic number for H is 1. Thus, one atom will contain one electron. As there are two atoms, so two electrons.
-The third molecule is $O_2^ + $. The atomic number for O is 8. Thus, one atom will contain eight electrons. As there are two atoms, so sixteen electrons. There is one positive charge. So, subtracting 1, we have 15 electrons.
-Thus, the number of electrons are -
$H_2^ + $= 1
${H_2}$= 2
$O_2^ + $= 15

Note: It must be added that if there are more than one atom of element, then the atomic number must be multiplied by the number of atoms. The positive charge comes when an electron is donated and the negative charge comes when an electron is accepted. So, the number of the electron changes when there is a sign on the atom.