Arrange the following metals in decreasing order of their atomic size: $Ca, Mg, Ba, Be$.

Write true or false for the statement: The term atomic size refers to the distance between the centre of the nucleus and the penultimate shell of an isolated atom.

What property do all elements in the same column of the Periodic Table as fluorine have in common?

Name:
$(a)$ three elements that have a single electron in their outermost shells.
$(b)$ two elements that have two electrons in their outermost shells.
$(c)$ three elements with filled outermost shells.

$(a)$ Electropositive nature of the element$(s)$ increases down the group and decreases across the period.
$(b)$ Electronegativity of the element decreases down the group and increases across the period.
$(c)$ Atomic size increases down the group and decreases across a period (left to right).
$(d)$ Metallic character increases down the group and decreases across a period.
On the basis of the above trends of the Periodic Table,answer the following about the elements with atomic numbers $3$ to $9$:
$(a)$ Name the most electropositive element among them.
$(b)$ Name the most electronegative element.
$(c)$ Name the element with the smallest atomic size.
$(d)$ Name the element which is a metalloid.
$(e)$ Name the element which shows maximum valency.

Arrange the following elements in the order of their increasing nonmetallic character:
$Li, O, C, Be, F$