| Term | Definition |
|---|
| Atom | the smallest part of material that cannot be broken up by chemicals. Each atom has a nucleus, containing protons, electrons and neutrons. Electrons orbit around. Atoms are made up mostly of empty space. |
| Element | a substance containing only one type of atom. |
| Compound | a substance made up of two or more different elements chemically combined in fixed ratios. They can be decomposed. |
| Molecule | two or more atoms chemically combined (the atoms can be the same or different). |
| Ion | an atom that has gained or lost electrons. An ion that has lost electrons becomes a cation (positive). An ion that has gained electrons becomes an anion (negative). |
| Valence electrons | the number of electrons in outer shell. |
| Valency | the number of electrons lost or gained. |
| Groups I, II, III | needs to lose electrons |
| Group IV | not ionic |
| Groups V, VI, VII | needs to gain electrons |
| Group 8 | noble gases->full outer shell thus exist as gases and do not react or bond with any other atom. |
| Electron | negative charge |
| Neutron | no charge |
| Proton | positive charge |
| The number of protons increases by one. | In the periodic table as you move from one atom to the next what is changing in the nucleus of each atom? |
| Metal | are groups one, two and three metal/non-metal? |
| Non-metal | are groups five, six and seven metal/non-metal? |
| Cation | positive ion |
| Anion | negative ion |
| VIII/noble gases/inert gases | stable group that does not need to gain or lose electrons |
| Most atoms need to either gain or lose electrons because they do not have a full outer shell. | Why do most atoms have to either gain or lose electrons? |
| Periods | these are the rows and they tell us how many shells the atoms have e.g 1st row has one shell, 2nd has two shells etc. |
| Groups | these are the columns of the periodic table and they tell us the valence electrons. |
| Atomic weight | neutrons + protons |
| Atomic Number | number of protons in the nucleus |
| Physical change | occurs when there is a change of state |
| Chemical change | occurs when a gas is given off, there is a permanent colour change, a precipitate forms, one metal deposists on another or there is a change in temperature. |
| Soluble | refers to something that can be dissolved |
| Insoluble | refers to something that cannot be dissolved |
| Aqueous | occurs when ionic substances are dissolved in H20 |
| Precipitate | refers to an insoluble solid that is formed in a chemical reaction |
| Supernatant | is the liquid which does not form a precipitate in a chemical reaction |
| that in a chemical reaction atoms can't be created or destroyed | the law of conservation of mass states that |
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