| A | B |
|---|
| elements | basic building blocks of all matter |
| Elements - pure substances | cannot be broken down into simpler substances |
| each element - special symbol | one or two letters |
| compound -substance formed by chemical combinations | of two or more elements |
| compounds can only be broken apart | by chemical reaction |
| Compounds have different properties | than the elements that make them up |
| symbols for compounds | chemical formula |
| subscripts | formula with numbers below the elements |
| subscripts in chemical formulas tell us | the number of particles that combine in a compound |
| Atom | smallest unit of an element that retains the properties of the element |
| protons, neutrons, electrons | 3 kinds of particles that atoms contain |
| atomic nucleus | tiny, dense body in atom's center |
| the # of protons in an atom | determines what the element is |
| # of known elements | 112 |
| some elements take part in | chemical reactions more easily than others |
| 3/4 of elements | metals |
| properties of metals | conduct electricity/heat well;shiny when polished;can be thin sheets-different shapes |
| 1869 Mendeleyev found properties of elements | went through repeating cycles |
| Groups in Mendeleyev's table contained | elements with similar chemical properties |
| Periodic table (Mendeleyev's) | named after periodic changes found in the elements' properties |
| molecules | particles with more than one atom joined together |
| molecules of elements | always contain only one kind of atom |
| compounds are made up of molecules | that have different kinds of atoms joined together |
| when a compound forms from elements | changes occur in the way the atoms are linked together |
| petroleum - complex mixture of | hydrocarbons |
| gasoline comes from | petroleum |
| plastics (polymers) | made of molecules with long chains of atoms |
