An element $X$ has a mass number of $35$ and the number of neutrons is $18$. Determine the atomic number and electronic configuration of $X$. Also, identify the group number, period number, and valency of $X$.

What is a metalloid? Name any two of them.

The electronic configurations of $4$ elements $A, B, C,$ and $D$ are as follows:
$A: 2, 1$
$B: 2, 2$
$C: 2, 8, 2$
$D: 2$
$(a)$ Which of these elements belong to the same group? Name them.
$(b)$ Which of these elements belong to the same period? Name them.
$(c)$ Which of these elements is inert? Name it.

Three elements $A$, $B$, and $C$ have $3$, $4$, and $2$ electrons respectively in their outermost shell. Determine the group number to which they belong in the Modern Periodic Table and state their valencies.

$(a)$ 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.

If an element $X$ is placed in group $14$,what will be the formula and the nature of bonding of its chloride?