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Matter and Energy
Unit 3 Lessons 1-2
Term | Definition |
---|---|
atom | the smallest particle into which an element can be divided and still be the same element. |
electron | negatively charged particles. |
nucleus | a small, dense center that has a positive charge and is surrounded by moving electrons. |
proton | positively charged particles in the nucleus. |
neutron | uncharged particles in the nucleus. |
electron cloud | an area around the nucleus. |
atomic number | the number of protons in the nucleus of an atom. |
mass number | the total number of protons and neutrons in an atom's nucleus. |
periodic table | an arrangement of the elements in order of their atomic numbers such that elements with similar properties fall in the same column, or group. |
chemical symbol | an abbreviation for the element's name. |
average atomic mass | the weighted average of the masses of all the naturally occurring isotopes of that element. |
metal | elements that are shiny and conduct heat and electricity well. |
nonmetal | poor conductors of heat and electricity. |
metalloid | elements that have some properties of metals and some properties of nonmetals. |
group | each vertical column of elements (from top to bottom) on the periodic table. |
period | each horizontal row of elements (from left to right) on the periodic table. |