Question

4) Examine each molecule below. Use the periodic table of the elements to find the name of each element. Then, identify each element present and the number of atoms for each.Molecule/Elements/Num. of Atoms NO2/Nitrogen & Oxygen /1 , 2 H2S/? / ? HCl /? /? NaCl /? / ? CaCO3/ ? /?

Answer 1

H2S/Hydrogen & Sulfur/ 2, 1

HCl/Hydrogen & Chlorine/ 1,1

NaCl/Sodium & Chlorine/ 1,1

CaCO3/ Calcium, Carbon & Oxygen/ 1,1,3

The molecular formulas as: H2S, HCl, etc. are indeed easy to read.

Just remember:

1. These formulas include the atomic symbols of each element that conforms the molecule. The atomic symbols are composed by one (e.g. H, S, C, O) or two (e.g. Na, Cl, Ca) latin letters and the first one will be always capitalized.

2. Following the atomic symbol could be a number which indicates the number of atoms of that element in the molecule. When no number appears after the symbol, it is assumed that there is only one atom of that element in the molecule.