The number of metalloids in the following elements are $Si$,$Mn$,$B$,$F$,$Cu$,$Ag$,$K$,$Sb$,$As$,$Na$,$Ge$.

As the atomic number increases in a group,the atomic density .........

Given below are two statements:
Statement-$I$: Along the period,the chemical reactivity of the elements gradually increases from group $1$ to group $18$.
Statement-$II$: The nature of oxides formed by group $1$ elements is basic,while that of group $17$ elements is acidic.
In the light of the above statements,choose the most appropriate answer from the options given below:

Among the statements $(I-IV)$,the correct ones are:
$(I)$ $Be$ has smaller atomic radius compared to $Mg$.
$(II)$ $Be$ has higher ionization enthalpy than $Al$.
$(III)$ Charge/radius ratio of $Be$ is greater than that of $Al$.
$(IV)$ Both $Be$ and $Al$ form mainly covalent compounds.

Which group element from the following achieves noble gas configuration after gaining two electrons?

The electronic configuration of an element is $1s^2, 2s^2 2p^6, 3s^2 3p^3$. What is the atomic number of the element which is just below the above element in the periodic table?