Answer:
ok just count the number of elements in each one…
UF4
1 U and 4 F
4+1 = 5
3Na2MoO4 = 3* (2Na + 1Mo + 4O) = 3* (2+1+4) = 7*3 = 21
BiOCl = 1 + 1 + 1 = 3
9 InN = 9* (1+1) = 9*2 = 18
NH4SCN = 1 + 4 + 1 + 1 + 1 = 8
5 * (3+4) = 5*7 = 35
NH4ClO3 = 1 + 4 + 1 + 3 = 9
NOHSO4 = 1 + 1 + 1 + 1 + 4 = 8
4H2 = 4*2 = 8
NbOCl3 = 1 + 1 + 3 = 5
3CF3SO3H = 3*(1 + 3 + 1 + 3 + 1) = 3*9 = 27
AgCNO = 1 + 1 + 1 + 1 = 4
6PbHAsO4 = 6 * (1 + 1 + 1 + 4) = 6*7 = 42
elements with more than one letter usually have the first letter uppercase, and the rest of the letters lowercase
such as Cl (Chlorine), As (Arsenic), Ag (silver)
whereas elements with only 1 letter just have that letter as a capital letter
such as H (hydrogen) S(sulfur) O(oxygen)
the letter behind the molecule/compound‘s formula is known as the coefficient.
for example, 4H2… 4 is the coefficient, so add the rest of the atoms and then multiply the whole thing by 4
2 atoms of hydrogen * 4 = 8
