c   Sp2 C carbonyl group 
c1  Sp C
c2  Sp2 C  
c3  Sp3 C
ca  Sp2 C in pure aromatic systems
cp  Head Sp2 C that connect two rings in biphenyl sys. 
cq  Head Sp2 C that connect two rings in biphenyl sys. identical to cp 
cc  Sp2 carbons in non-pure aromatic systems
cd  Sp2 carbons in non-pure aromatic systems, identical to cc
ce  Inner Sp2 carbons in conjugated systems
cf  Inner Sp2 carbons in conjugated systems, identical to ce
cg  Inner Sp carbons in conjugated systems
ch  Inner Sp carbons in conjugated systems, identical to cg
cx  Sp3 carbons in triangle systems
cy  Sp3 carbons in square systems
cu  Sp2 carbons in triangle systems
cv  Sp2 carbons in square systems
h1  H bonded to aliphatic carbon with 1 electrwd. group  
h2  H bonded to aliphatic carbon with 2 electrwd. group 
h3  H bonded to aliphatic carbon with 3 electrwd. group 
h4  H bonded to non-sp3 carbon with 1 electrwd. group 
h5  H bonded to non-sp3 carbon with 2 electrwd. group 
ha  H bonded to aromatic carbon  
hc  H bonded to aliphatic carbon without electrwd. group 
hn  H bonded to nitrogen atoms
ho  Hydroxyl group
hp  H bonded to phosphate 
hs  Hydrogen bonded to sulphur 
hw  Hydrogen in water 
hx  H bonded to C next to positively charged group  
f   Fluorine
cl  Chlorine 
br  Bromine 
i   Iodine 
n   Sp2 nitrogen in amide groups
n1  Sp N  
n2  aliphatic Sp2 N with two connected atoms 
n3  Sp3 N with three connected atoms
n4  Sp3 N with four connected atoms 
na  Sp2 N with three connected atoms 
nb  Sp2 N in pure aromatic systems 
nc  Sp2 N in non-pure aromatic systems
nd  Sp2 N in non-pure aromatic systems, identical to nc
ne  Inner Sp2 N in conjugated systems
nf  Inner Sp2 N in conjugated systems, identical to ne
nh  Amine N connected one or more aromatic rings 
no  Nitro N  
o   Oxygen with one connected atom
oh  Oxygen in hydroxyl group
os  Ether and ester oxygen
ow  Oxygen in water 
p2  Phosphate with two connected atoms 
p3  Phosphate with three connected atoms, such as PH3
p4  Phosphate with three connected atoms, such as O=P(CH3)2
p5  Phosphate with four connected atoms, such as O=P(OH)3
pb  Sp2 P in pure aromatic systems 
pc  Sp2 P in non-pure aromatic systems
pd  Sp2 P in non-pure aromatic systems, identical to pc
pe  Inner Sp2 P in conjugated systems
pf  Inner Sp2 P in conjugated systems, identical to pe
px  Special p4 in conjugated systems
py  Special p5 in conjugated systems
s   S with one connected atom 
s2  S with two connected atom, involved at least one double bond  
s4  S with three connected atoms 
s6  S with four connected atoms 
sh  Sp3 S connected with hydrogen 
ss  Sp3 S in thio-ester and thio-ether
sx  Special s4 in conjugated systems
