What is the position of metalloids in the periodic table?

An element is placed in $2^{nd}$ Group and $3^{rd}$ Period of the Periodic Table,burns in the presence of oxygen to form a basic oxide.
$(a)$ Identify the element.
$(b)$ Write the electronic configuration.
$(c)$ Write the balanced chemical equation when it burns in the presence of air.

An element $X$ of group $15$ exists as a diatomic molecule and combines with hydrogen at $773 \, K$ in the presence of a catalyst to form a compound,ammonia,which has a characteristic pungent smell.
$(a)$ Identify the element $X$. How many valence electrons does it have?
$(b)$ Draw the electron dot structure of the diatomic molecule of $X$. What type of bond is formed in it?
$(c)$ Draw the electron dot structure for ammonia and what type of bond is formed in it?

Can the following groups of elements be classified as Dobereiner's triad?
$(a)$ $Na, Si, Cl$
$(b)$ $Be, Mg, Ca$
Atomic mass of $Be = 9, Na = 23, Mg = 24, Si = 28, Cl = 35, Ca = 40$. Explain by giving reasons.

Three elements $X$,$Y$,and $Z$ having atomic numbers $11$,$7$,and $6$ respectively react with oxygen to form their oxides.
$(a)$ Arrange these oxides in increasing order of their basic nature.
$(b)$ Give reason for your answer.

Name any two pairs of elements which were adjusted by Newlands in the same slot.