Compounds and Chemical Formulas

ELEMENTS - Review a pure substance that cannot be separated into simpler substances made of all the same atoms Identified by it’s atomic # (# of protons) valence electrons determines conductivity and reactivity. The 1 st letter in chemical symbol is always capitalized. If there is a 2 nd letter, it is always lowercase. 13 Al Aluminum

Molecule vs Compound Molecule: – substance made of 2 or more atoms – Can be the same or different elements – Ex: O 2 and CH 4 Compound – Substance made of 2 or more different elements – Ex: CH 4 and H 2 O – Organic compounds contain carbon, hydrogen, nitrogen and oxygen

Short way to show how many atoms of each element are in a compound Letters are the symbol of the element Numbers tell you the amount of atoms Chemical Formula

The little number down and to the right of the element symbol that tell us how many atoms there are of that element. – If there is no subscript, then it’s understood as 1 atom of that element. – Subscripts in a formula can’t change without changing the substance Example: H 2 O is water, H 2 O 2 is hydrogen peroxide Subscript

How many elements? – Count the capitals How many atoms? – Look at the subscripts (remember, if there is no subscript, then it’s 1 atom) How many? CaCo CaCO 3 2 elements: Calcium (Ca) & Cobalt (Co) 1 atom of Ca 1 atom of Co 3 elements: Calcium (Ca), Carbon (C), and Oxygen (O) 1 atom of Ca 1 atom of C 3 atoms of O

Make this chart in your journal Compound NamesChemical FormulaDrawing Sodium Chloride Calcium Oxide Calcium Chloride Carbon Dioxide Aluminum Oxide

Use the pieces to make models of the 5 compounds that are listed in your chart. You will find clues to the names of the 2 elements that make up that compound. Remember to use the patterns of the pieces just like putting together a jigsaw puzzle. Write the chemical formula in the chart for each compound. Compound Puzzle Pieces

Answers Compound NamesChemical FormulaDrawing Sodium ChlorideNaCl 1 atom of Na 1 atom of Cl Calcium OxideCaO 1 atom of Ca 1 atom of O Calcium ChlorideCaCl 2 1 atom of Ca 2 atoms of Cl Carbon DioxideCO 2 1 atom of C 2 atoms of O Aluminum OxideAl 2 O 3 2 atoms of Al 3 atoms of O

Molecular Models Use the instruction sheet.

Practice – Writing Chemical Formulas 1.Magnesium sulfate = 1 atom of magnesium + 1 atom of sulfur + 4 atoms of oxygen 2.Potassium chloride = 1 atom of potassium + 1 atom of chlorine 3.Glucose = 6 atoms of carbon + 12 atoms of hydrogen + 6 atoms of oxygen 4.Baking soda = 1 atom of sodium + 1 atom of hydrogen + 1 atom of carbon + 3 atoms of oxygen

Write the chemical formula for these compounds.

The big number in front of the chemical formula that tell us how many molecules of that compound are present. – We MULTIPLY the coefficient with the subscripts from each element to count the atoms. – Unlike subscripts, this number can change without changing the substance Coefficient How many Hydrogen atoms? 4 2 How many oxygen atoms?

Coefficient Practice: How many atoms are present? Carbon: 2 atoms Hydrogen: 8 atoms Hydrogen: 2 atoms Chlorine: 2 atoms Hydrogen: 4 atoms Oxygen: 4 atoms

Parentheses are used to indicate elements grouped together as a molecule within a compound. – Just like in math, you MULTIPLY how many atoms of each element inside with the number outside. Parentheses Ca H O H O Calcium: 1 atom Oxygen: 2 atoms Hydrogen: 2 atoms

Write the chemical formulas from the drawings

Make drawings from the chemical formulas 3 CO 2 2 CaSO 3 2 Ca(OH) 2

Practice Analyzing Chemical Formulas Practice w/s