Question

Write the name from the descriptions.
Two elements having valency four.

Answer 1

Hint Valency is the combining capacity of an atom that can also be defined as the number of bonds that an atom can form as part of a compound is expressed by the valency of that element. It gives us an idea of valence electrons.

Complete Step by step solution:
We know that electrons in an atom are arranged in shells or orbitals. Valence electrons are those electrons which are present in the outermost shell of an atom and Bohr-bury scheme suggested that at most eight electrons are present in the outermost shell of an atom. A number of these valence electrons are valencies of that element.
If in an element there are 1,2,3 and 4 electrons present in the outermost shell then their valency is also 1,2,3 and 4. If electrons present in the outermost shell is 5,6,7 and 8 then valence electrons can be calculated by subtracting from 8 i.e. for 5 the valency will be 8-5=3, 2, 1 and 0 respectively.
The elements which have valency two are those elements which have 2 or 6 electrons in their outermost shell. The example of elements having valency 2 is Beryllium having atomic number 4 and electrons distribution is 2,2 so this shows valency 2 and another example is magnesium having atomic number 12 whose electrons are distributed as 2,8,2 i.e. outermost 2 electrons so it also shows valency of 2.
Hence magnesium and beryllium show the valency of two.

Note: Elements that have valency exactly 0 these are termed as stable elements that they do not take part in any type of ion formation, generally noble gas shows stability and have zero valencies. Valency is a dimensionless quantity.