Write Lewis dot symbols for atoms of the following elements: $Mg, Na, B, O, N, Br$.

Which of the following statements is true with respect to $H_2O$,$NH_3$ and $CH_4$?
$A.$ The central atoms of all the molecules are $sp^3$ hybridized.
$B.$ The $H-O-H$,$H-N-H$ and $H-C-H$ angles in the above molecules are $104.5^{\circ}$,$107.5^{\circ}$ and $109.5^{\circ}$ respectively.
$C.$ The increasing order of dipole moment is $CH_4 < NH_3 < H_2O$.
$D.$ Both $H_2O$ and $NH_3$ are Lewis acids and $CH_4$ is a Lewis base.
$E.$ $A$ solution of $NH_3$ in $H_2O$ is basic. In this solution,$NH_3$ and $H_2O$ act as a Lowry-Bronsted base and acid respectively.
Choose the correct answer from the options given below:

Which of the following has been arranged in order of decreasing bond length?

$A$ lone pair of electrons in an atom implies

In the following electron dot structure,the correct calculation of the formal charge on the nitrogen atoms from left to right is $\overset{\centerdot \centerdot}{\mathop{N}}\text{=}\mathop{N}\text{=}\overset{\centerdot \centerdot}{\mathop{N}}$

Which of the following pairs does not contain isoelectronic species?