Two elements $X$ and $Y$ have atomic numbers $11$ and $16$ respectively.
$(a)$ Write the electronic configuration of both.
$(b)$ Which type of bond will they form?
$(c)$ Write the formula of the compound formed by their combination (in terms of $X$ and $Y$).

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.

Which of the following statements about the Modern Periodic Table is correct?

Name the following:
$(a)$ $A$ metal that can be cut with a knife.
$(b)$ $A$ metal that is liquid at room temperature.
$(c)$ $A$ metal that has $3$ valence electrons.

An element $X$ of group $15$ exists as a diatomic molecule and combines with hydrogen at $773 \, K$ in the presence of a catalyst to form a compound,ammonia,which has a characteristic pungent smell.
$(a)$ Identify the element $X$. How many valence electrons does it have?
$(b)$ Draw the electron dot structure of the diatomic molecule of $X$. What type of bond is formed in it?
$(c)$ Draw the electron dot structure for ammonia and what type of bond is formed in it?

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.