A

Any (any atom except hydrogen)

AH

Any atom, including hydrogen

Q

Hetero (any atom except hydrogen and carbon)

QH

Hetero atom or hydrogen (any atom except carbon)

M

Metal (contains alkali metals, alkaline earth metals, transition metals, actinides, lanthanides, poor(basic) metals, Ge, Sb and Po)

MH

Metal or hydrogen

X

Halogen (F,Cl,Br or I)

XH

Halogen or hydrogen