If two different non-axial $d-$orbitals having $xz$ nodal plane form $\pi-$bond by overlapping each other,then the internuclear axis will be:

In the Lewis dot structure for $NO_2^-$,the total number of valence electrons around the nitrogen atom is $.......$

Fill in the blanks given below:
$(i)$ The attractive force which holds atoms,molecules,and ions together is called ......... .
$(ii)$ First of all,............ and ............ scientists provided detailed information about valency.
$(iii)$ In the structure of an atom,when only the electrons of the outermost shell participate,they are known as ............ .
$(iv)$ The symbol used to represent valence electrons in an atom is called ........ .

Which one of the following molecules contains both ionic and covalent bonds?

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

The total number of lone pairs of electrons in $N_2O_3$ is