Write true or false for the statement: In order to fit elements into his table,Newlands adjusted three elements in the same slot,but also put some unlike elements in the same slot.

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.

Give an account of the process adopted by Mendeleev for the classification of elements. How did he arrive at Periodic Law?

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.

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 the major air pollutants.
$(a)$ Identify the element $X$
$(b)$ Write the electronic configuration of $X$
$(c)$ Write the balanced chemical equation for the thermal decomposition of ferrous sulphate crystals?

An element $X$ (atomic number $17$) reacts with an element $Y$ (atomic number $20$) to form a divalent halide.
$(a)$ What will be the nature of oxide of element $Y$? Identify the nature of bonding in the compound formed.
$(b)$ Draw the electron dot structure of the divalent halide.