Question

Calculate number of electrons in $ 1.4g $ $ {}_7{N^{3 - }} $ ion.

Answer 1

Hint: Valence shell: The shell which is at the last of the electronic configuration, is known as valence shell and the number of electrons present in the valence shell is known as valence electrons and they decide the valency of an atom.

Complete step by step solution:
Let us first talk about what atoms are.
Atoms: They are defined as the smallest particle of any substance. They cannot be broken into pieces further. Atoms consist of three types of elements i.e. electrons, protons and neutrons.
Element: It is defined as the smallest part of any substance. They are made of the same type of atoms. They are basically of two types i.e. metals and non-metals. For example: hydrogen, carbon, oxygen, etc.
Molecule: The substance which is formed by the same type of elements i.e. same metals or same non-metal. For example: hydrogen molecule i.e. $ {H_2} $ (which is made of two hydrogen atom), oxygen molecule i.e. $ {O_2} $ (which is made of two oxygen atoms), etc.
One atom of an element contains number of electrons equal to its atomic number but the number of electrons in an ion is different the number of electron in positively charged ion is equal to the atomic number minus the charge on the ion and the number of electrons in a negatively charged ion will be atomic number plus the charge on the ion. And one mole of an atom contains $ 6.022 \times {10^{23}} \times $ atomic number electrons.
Here we are given with $ 1.4g $ $ {}_7{N^{3 - }} $ ion. So the number of moles (ratio of given mass to the molecular mass) will be $ \dfrac{{1.4}}{{14}} = 0.1 $ . As one mole contains $ 6.022 \times {10^{23}} \times 10 $ electrons hence $ 0.1 $ moles will contain $ 6.022 \times {10^{23}} \times 10 \times 0.1 $ . Hence the total number of electrons in $ 1.4g $ $ {}_7{N^{3 - }} $ ion is $ 6.022 \times {10^{23}} $ .

Note:
Compound: The substance which is formed by two or more different elements are known as compounds. For example: water i.e. $ {H_2}O $ (which is made of two hydrogen elements and one oxygen element), carbon dioxide i.e. $ C{O_2} $ (which is made of two oxygen and one carbon atom), etc.