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 is meant by 'group' in the modern periodic table? How do the following change on moving from top to bottom in a group?
$(i)$ Number of valence electrons
$(ii)$ Number of occupied shells
$(iii)$ Size of atoms
$(iv)$ Metallic character of elements
$(v)$ Effective nuclear charge experienced by valence electrons.

Write the formula of the product formed when the element $A$ (atomic number $19$) combines with the element $B$ (atomic number $17$). Draw its electronic dot structure. What is the nature of the bond formed?

The atomic number of an element is $17$. Predict $(a)$ its valency,$(b)$ whether it is a metal or non-metal,$(c)$ its relative size with respect to other members of its group. Justify your answer in each case.

Arrange the following elements in the order of their increasing non-metallic character: $Li, O, C, Be, F$.

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.