The correct order of bond strength for the given species is:

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

$CO$ has the same number of electrons as which of the following ions? Or,which ion is isoelectronic with $CO$?

In which of the following pairs of species is the bond length as well as the bond energy of the $I^{st}$ species less than the $II^{nd}$ species?

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 ........ .

The isoelectronic pair is