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.

$(a)$ Predict which of the following will form anions and which will form cations:
$(i)$ $Na$ $(ii)$ $Al$ $(iii)$ $Cl$ $(iv)$ $O$
$(b)$ Name two elements that are inert.

Which of the following sets of elements is written in the order of their increasing metallic character?

$(i)$ The elements of the second period along with their atomic numbers in parentheses are given below: $B(5)$,$Be(4)$,$O(8)$,$N(7)$,$Li(3)$,$C(6)$,$F(9)$.
$(a)$ Arrange them in the same order as they appear in the periodic table.
$(b)$ Which element has the largest and smallest atom?
$(ii)$ Why does the atomic radius change as we move from left to right in a period?

In Mendeleev's Periodic Table,gaps were left for elements to be discovered later. Which of the following elements found a place in the periodic table later?

Taking the example of an element of atomic number $16$, explain how the electronic configuration of the atom of an element relates to its position in the modern periodic table and how valency of an element is calculated on the basis of its atomic number.