1. Chemical Formulas By: Mr. Castillo & Mr. Buenrostro

2. 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.

3. 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. C 6 H 12 O 6: Glucose

4. Chemical Formulas Chemical formula: identify substances and determines the number of atoms of each element. Example: CH 4, CO 2, H 2 O, H 2 O 2

5. Formula symbols Elements are written with letter symbols CO: 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

6. Subscripts Subscript: lower (bottom) number that determines the number of atoms in a formula. C 2 H 3 : C= 2 atom, H= 3 atoms H 2 SO 4: H= 2 atoms, S= 1 atom, O= 4 atoms If no subscript number is present the elements value is 1; as in S above.

7. 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.

8. Determine the number of elements and atoms present in each formula. CH 3 C= 1 atom H= 3 atoms 2 elements HCl H= 1 atom Cl= 1 atom 2 elements H 2 SO 4 H= 2 atom S= 1 atom O= 4 atom 3 elements Formula Practice

9. Review Any questions???