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

An element is placed in $2^{nd}$ Group and $3^{rd}$ Period of the Periodic Table. It burns in the presence of oxygen to form a basic oxide.
$(a)$ Write a balanced chemical equation when this oxide is dissolved in water.
$(b)$ Draw the electron dot structure for the formation of this oxide.

Properties of the elements are given below. Where would you locate the following elements in the periodic table?
$(a)$ An element which is an inert gas with atomic number $2$.
$(b)$ An element whose thin oxide layer is used to make other elements corrosion resistant by the process of 'anodising'.

An element $X$,which is a yellow solid at room temperature,shows catenation and allotropy. $X$ forms two oxides which are also formed during the thermal decomposition of ferrous sulphate crystals and are major air pollutants.
$(a)$ What would be the nature (acidic/basic) of the oxides formed?
$(b)$ Locate the position of the element in the Modern Periodic Table.

Why are lithium (atomic number $3$) and potassium (atomic number $19$) placed in group $1$? What will be the atomic numbers of the first two elements in group $2$?

The elements $Be$,$Mg$,and $Ca$,each having two electrons in their outermost shells,are in periods $2$,$3$,and $4$ respectively of the modern periodic table. Answer the following questions,giving justification in each case:
$(i)$ Write the group to which these elements belong.
$(ii)$ Name the least reactive element.
$(iii)$ Name the element having the largest atomic radius.