Which one of the following elements exhibits the maximum number of valence electrons?

Which of the given elements $A, B, C, D$ and $E$ with atomic numbers $2, 3, 7, 10$ and $30$ respectively belong to the same period?

The atomic numbers of a few elements are given below: $10, 20, 7, 14$.
$(a)$ Identify the elements.
$(b)$ Identify the group number of these elements in the Periodic Table.
$(c)$ Identify the periods of these elements in the Periodic Table.

Write true or false for the statement: Metallic character decreases across a period and increases down a group because the effective nuclear charge acting on the valence shell electrons increases across a period and decreases down the group.

Arrange the following elements in increasing order of their atomic radii.
$(a)$ $Li, Be, F, N$
$(b)$ $Cl, At, Br, I$

$(a)$ In this ladder (Figure),symbols of elements are jumbled up. Rearrange these symbols of elements in the increasing order of their atomic number in the Periodic Table.
$(b)$ Arrange them in the order of their group also.