Question

Three elements A, B, and C have 3, 4, and 2 electrons respectively in their outermost shell. Give the group number to which they belong in the Modern Periodic Table. Also, give their valencies.

Answer 1

Valency and Valence electrons:

• Valency is termed as the property of an element determining the number of atoms with which it can combine.
• It is a direct reflection of the number of electrons present in the outermost shell of the element which can be called valence electrons.

Classification of the given elements:

• The element ‘A ’ belongs to Group 13 of the periodic table since it possesses 3 valence electrons.Element ‘A’ can be Boron($\mathrm{B}$), Aluminium($\mathrm{Al}$), Gallium($\mathrm{Ga}$), Indium($\mathrm{In}$), Thallium($\mathrm{Tl}$) and Nihonium($\mathrm{Nh}$). Element ‘A’ has a valency of 3 as it belongs to Group 13 of the periodic table.
• The element ‘B ’ belongs to Group 14 of the periodic table since it possesses 4 valence electrons.Element ‘B’ can be Carbon($\mathrm{C}$), Silicon($\mathrm{Si}$), Germanium($\mathrm{Ge}$), Tin($\mathrm{Sn}$), Lead($\mathrm{Pb}$), and Flerovium($\mathrm{Fl}$) . Element ‘B’ has a valency of 4 as it belongs to Group 14 of the periodic table.
• The element ‘C ’ belongs to Group 2 of the periodic table since it possesses 2 valence electrons.Element ‘C’ can be Beryllium($\mathrm{Be}$), Magnesium($\mathrm{Mg}$), Calcium($\mathrm{Ca}$), Strontium($\mathrm{Sr}$),Barium($\mathrm{Ba}$), and Radium($\mathrm{Ra}$). Element ‘C’ has a valency of 2 as it belongs to Group 2 of the periodic table.

Representation of elements in Tabular form:

Element	Group Number	Valency
A	Group 13	3
B	Group 14	4
C	Group 2	2