An element belongs to the third period and second group of the periodic table:
$(a)$ State the number of valence electrons in it.
$(b)$ Is it a metal or a non-metal?
$(c)$ Name the element.
$(d)$ Write the formula of its oxide.

The atomic radii of the elements of the second period are given below:

Second period elements	$B$	$Be$	$O$	$N$	$Li$	$F$	$C$
Atomic Radii $(pm)$	$88$	$111$	$66$	$74$	$152$	$64$	$77$

$(i)$ Arrange these elements in decreasing order of their atomic radii.
$(ii)$ Are the elements now arranged in the pattern of a period in the periodic table?
$(iii)$ Name the element which has the $(a)$ smallest and $(b)$ largest atomic number.
$(iv)$ From the above data, infer how the atomic size or atomic radius of the elements changes as we move from left to right in a period.
$(v)$ Name one metal, one non-metal, and a metalloid out of these elements.
$(vi)$ Why does atomic radius decrease as we move from left to right in a period?

Mention any two trends exhibited by elements when we go from left to right across the period of the periodic table.

$(a)$ How does electropositivity of elements get affected as we move :
$(i)$ down a group
$(ii)$ across a period?
$(b)$ Which atomic property increases both as we move across a period or down a group?

By considering their position in the Periodic Table,which one of the following elements would you expect to have maximum metallic characteristic?
$Ga$,$Ge$,$As$,$Se$,$Be$

$K$ and $Ca$ have atomic numbers $19$ and $20$ respectively,and they belong to the same period.
$(a)$ Which among them would have a smaller atomic size?
$(b)$ Which one would be more electropositive?
$(c)$ To which group would each of them belong?