Chemical Formulas

By: Mr. Castillo & Mr. Buenrostro

Chemical Formulas

• We previously learned compounds are made of two or more different elements.

• Also, that molecules are the smallest unit of a compound.

• With the periodic table of elements we learned the chemical symbols or letters.

• Now, we will learn how to read compounds by learning about the chemical language made of chemical words called Formulas.

Chemical Formulas• Chemical formula: shorthand method for

writing the number of atoms and type of elements in a compound.

• A chemical formula is a recipe for a substance.C6H12O6: Glucose

Chemical Formulas• Chemical formula: identify substances and

determines the number of atoms of each element.

• Example: CH4, CO2, H2O, H2O2

Formula symbols

• Elements are written with letter symbolsCO: C= carbon, O= oxygen

HI: H= hydrogen, I= Iodine• The first letter is always uppercase. The

second letter is lowercase.HCl: H= hydrogen, Cl= chlorine

Subscripts

• Subscript: lower (bottom) number that determines the number of atoms in a formula.

• C2H3: C= 2 atom, H= 3 atoms• H2SO4: H= 2 atoms, S= 1 atom, O= 4 atoms• If no subscript number is present the

elements value is 1; as in S above.

Subscripts

• Subscript: Below, under, or beneath• A subway station is below ground.• A submarine is under water.• A subatomic particle is below the Atoms level.

• Determine the number of elements and atoms present in each formula.

• CH3

C= 1 atom H= 3 atoms 2 elements• HCl

H= 1 atom Cl= 1 atom 2 elements• H2SO4

H= 2 atom S= 1 atom O= 4 atom 3 elements

Formula Practice

Review

• Any questions???