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8th Science U3
Introduction to Chemistry
Term | Definition |
---|---|
nucleus | an atom's central region, which is made up of protons and neutrons |
protons | a subatomic particle that has a positive charge and that is located in the nucleus of an atom; the number of protons in the nucleus is the atomic number, which determines the identity of an element. |
electrons | a subatomic particle that has a negative charge |
neutrons | a subatomic particle that has no charge and that is located in the nucleus of an atom |
electron cloud | a region around the nucleus of an atom where electrons are likely to be found. |
atomic number | the number of protons in the nucleus of an atom; the atomic number is the same for all atoms of an element. |
mass number | the sum of the numbers of protons and neutrons in the nucleus of an atom. |
atom | the smallest unit of an element that maintains the properties of that element. |
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 | a one-, two-, or three-letter abbreviation of the name of an element |
average atomic mass | the weighted average of the masses of all naturally occurring isotopes of an element |
metal | an element that is shiny and that conducts heat and electricity well. |
nonmetal | an element that conducts heat and electricity poorly |
metalloid | an element that has properties of both metals and nonmetals. |
group | a vertical column of elements in the periodic table; elements in a group share chemical properties. |
period | a horizontal row of elements in the periodic table. |
chemical bond | an interaction that holds atoms or ions together. |
valeence electron | an electron that is found in the outermost shell of an atom and that determines the atom's chemical properties. |