CompoundsCompounds

Review:Review: Element:Element: - pure substance that cannot be broken down pure substance that cannot be broken down

into a simpler substance by ordinary chemical into a simpler substance by ordinary chemical changes.changes.

- consists of atoms of only one type.consists of atoms of only one type.- Combine in specific ways to form new Combine in specific ways to form new

substances due to the electron levels.substances due to the electron levels.- The combination forms bonds between the The combination forms bonds between the

atoms, producing a atoms, producing a compoundcompound..

Properties of compounds:Properties of compounds: depends on which atoms it containsdepends on which atoms it contains how the atoms are arrangedhow the atoms are arranged often very different from the elements often very different from the elements

that make themthat make themExamples: water, HExamples: water, H22OO

salt, NaClsalt, NaCl

Compounds continued…Compounds continued… Compounds always contain atoms of Compounds always contain atoms of

elements in a specific ratio.elements in a specific ratio.Example:Example:Ammonia, 3:1, hydrogen to nitrogenAmmonia, 3:1, hydrogen to nitrogenHydrazoic acid, 1:3, hydrogen to nitrogenHydrazoic acid, 1:3, hydrogen to nitrogenMethane, 1:4, carbon to hydrogenMethane, 1:4, carbon to hydrogenPropane, 3:8, carbon to hydrogenPropane, 3:8, carbon to hydrogen

Different Compounds:Different Compounds: The same elements can form different The same elements can form different

compounds.compounds.Example:Example:

Water, HWater, H22OO

Hydrogen peroxide, HHydrogen peroxide, H22OO22

Chemical Formulas:Chemical Formulas: An expression that shows the number An expression that shows the number

and types of atoms joined in a and types of atoms joined in a compound.compound.

Example:Example:Carbon dioxide, COCarbon dioxide, CO22, 1:2 ratio, 1:2 ratio

Carbon monoxide, CO, 1:1 ratioCarbon monoxide, CO, 1:1 ratioGlucose, CGlucose, C66HH1212OO66, 6:12:6 or 1:2:1 ratio, 6:12:6 or 1:2:1 ratio

Chemical Formulas Chemical Formulas con’t…con’t…

Note: If the chemical formula does NOT Note: If the chemical formula does NOT have a subscript in it, it is understood as have a subscript in it, it is understood as a 1:1 ratio.a 1:1 ratio.

Example:Example: NaCl, HClNaCl, HCl