The document provides an overview of chemical compounds, including definitions and examples such as H2O and NaCl. It explains chemical formulas and how to count atoms using subscripts and parentheses. Additionally, it includes exercises for identifying elements and their atom counts in given molecules.

4. •COMPOUND
•- a substance made of two or more
different elements that are
chemically combined
•Examples: H2O, CO2,
NaCl,C6H12O6

5. Chemical Formulas
•Chemical formulas show the number of
atoms of each element present.
•Example: H2SO4 - (Sulfuric Acid)
•Hydrogen- 2
•Sulfur- 1
•Oxygen- 4

13. (CH3)2CO
•Carbon – 3
•Hydrogen – 6
•Oxygen - 1

14. COUNTING ATOMS
1. Complete the sentences below. You can choose the answer from the set of words provided inside the textbox.
a) The ________________ which are represented by a single uppercase letter, or represented by an uppercase letter
followed by a lowercase letter. This tells you the types of elements in the compound.
b) The ________________ which are numbers that are found on the lower ________________- hand side of each
element symbol. This tells you the number of ________________of this element in the molecule. If an element
symbol has no subscript next to it, then this indicates that there is only ________________ atom of this element in the
molecule.
c) The ________________ which surround some groups of atoms indicate that the numbers of all of the atoms inside it
need to be ________________ by the ________________ on the outside of the parenthesis found on the lower
________________ - hand side of that parenthesis.
atoms one subscript right multiplied parenthesis subscripts right symbols

15. 1) NaOH 2) HNO3 3) 2 Li2O
Element # of Atoms Element # of Atoms Element # of Atoms
2. Identify the element present in the molecule
below and record the number of atom of each.