The electrically neutral mononuclear hydrides of group 14 having two non-bonding electrons, the electrically neutral mononuclear hydrides of group 15 having four non-bonding electrons, and also the compound HB:. The names of a number of these are shown below.
 

RB:	boranylidenes	RAs:	arsanylidenes
RN:	nitrenes	R2Sn:	stannylidenes
R2Si:	silylenes	RSb:	stibanylidenes
RP:	phosphanylidenes	R2Pb:	plumbylidenes
R2Ge:	germylidenes

Note that if R = H, these compounds are parent hydrides; derivatives formed by substitution are named accordingly. However, if the substituent's first atom, bearing the free @[email protected], is of the same element as the atom of the carbene analogue, other parent compounds may be required (see @[email protected] ), e.g. HN: nitrene; CH₃N: methylnitrene; H₂NN: @[email protected] (synonym @[email protected], not @[email protected]).