What is an element? An element is a pure substance that cannot be separated or broken down into simpler substances by physical or chemical means. Each element contains only 1 type of atom All the elements are arranged on the periodic table by their atomic number (# of protons). Examples: C, H, Br, Co, He, S
What is a compound? A compound is a substance that is made up of 2 or more elements that are chemically combined . In order for elements to combine, they must react, or undergo A chemical change. What is a chemical change? Some examples? + = Sodium – is a soft, silvery white metal that reacts violently with water Chlorine – is a poisonous greenish yellow gas. Table Salt (NaCl)
So Na + Cl = NaCl which is table salt. This is an example of a compound. Sodium and chlorine chemically combined to form a totally new substance with different properties than the original substances. Some other examples of compounds: H 2 O 2 HCl H 2 O NaOH CH 4
What are mixtures? A mixture is a combination of 2 or more substances that are NOT chemically combined. Examples: Pizza, salt water
Element, Compound or Mixture?? Hydrogen C NaOH Helium Air F Kool-aid HF NaBr
How can you tell how many atoms of each kind of element there are in a compound?? How many atoms of oxygen are in one molecule of citric acid? C 6 H 8 O 7 How many atoms are there in one molecule of citric acid?
How many atoms are there in one molecule of menthol? C 10 H 20 O See “Number of Atoms in a Formula” worksheet
Figure out the total amount of atoms in each compound: 2H 2 O