Question

The valency of Aluminium is \[3\] . Write the valency of other radicals present in the following compounds.
A.Aluminium chloride
B.Aluminium oxide
C.Aluminium nitride
D.Aluminium sulphate

Answer 1

Hint: The valency of an element indicates the number of electrons present in the outermost shell of an atom. It is the combining power of an element with another atom. In other words, the number of bonds that an atom can form is expressed by the valency of the element.

Complete answer:
We already know that electrons are present in the shells/orbitals of an atom. The electrons present in the outermost shell of an atom are termed as valence electrons. And the valency of an element indicates the number of electrons present in the outermost shell. It is the combining capacity of an element when it forms a chemical bond with the other element. According to the Bohr-bury concept, the outermost shell can contain a maximum of eight electrons. When the outermost shell is completely filled, its combining capacity becomes zero i.e. it becomes inert for example- in case of noble gases like Helium, Argon etc.
The valency can be predicted by looking at the group number of the element in the periodic table. Elements in the same group have the same valency in the periodic table.
In this question, the valency of Aluminium is given i.e. \[3\]
Let’s determine the valency of other radicals in the given compound,
A. Aluminium Chloride
Chemical formula- \[AlC{l_3}\]
Other radical is chloride- \[C{l^ - }\]
Valency of chloride= \[1\]

B. Aluminium Oxide
Chemical formula- \[A{l_2}{O_3}\]
Other radical is oxide- \[{O^{2 - }}\]
Valency of oxide = \[2\]

C. Aluminium Nitride
Chemical formula- \[Al\,N\]
Other radical is nitride- \[{N^{3 - }}\]
Valency of nitride = \[3\]

D. Aluminium Sulphate
Chemical formula- \[A{l_2}{(S{O_4})_3}\]
Other radical is sulphate- \[S{O_4}^{2 - }\]
Valency of sulphate = \[2\]
This is how we determine the valency of an element in any compound.

Note:
Remember valency is always a whole number. It has no plus or minus sign. It is the number of electrons of an element which can lose or gain to attain stability. The valency of an element is its group number only.