Aluminium reacts with $NaOH$ and forms compound '$X$'. If the coordination number of aluminium in '$X$' is $6$, the correct formula of $X$ is:

Give the origin and occurrence of group $13$ elements.

Given below are two statements: One is labelled as Assertion $A$ and the other is labelled as Reason $R$:
Assertion $A$ : The stability order of $+1$ oxidation state of $Ga$,$In$ and $Tl$ is $Ga < In < Tl$.
Reason $R$ : The inert pair effect stabilizes the lower oxidation state down the group.
In the light of the above statements,choose the correct answer from the options given below :

Which of the following elements form dimeric halides?

The correct statements from the following are:
$(A)$ Ionic radii of trivalent cations of group $13$ elements decrease down the group.
$(B)$ Electronegativity of group $13$ elements decreases down the group.
$(C)$ Among the group $13$ elements, Boron has the highest first ionisation enthalpy.
$(D)$ The trichlorides and triiodides of group $13$ elements are covalent in nature.
Choose the correct answer from the options given below:

Describe the chemical properties of the elements of group $13$.