| A | B |
|---|
| atom | the smallest particle of an element |
| atomic mass | the average mass of one atom of an element |
| activation energy | the minimum amount of eneregy needed to start a chemical reaction |
| atomic number | the number of protons in the nucleus of an atom |
| atomic mass unit(amu) | the unit of measurement for the mass of particles in atoms |
| catalyst | a material that increases the rate of a chemical reaction by lowering the activation energy |
| chemical reaction | a process in which substances undergo chemical changes |
| compound | a substance made of two or more elements chemically combined |
| chemical equation | a short easy way to show chemical reactions, using symbols instead of words |
| conservation of mass | the principal stating matter is not created or destroyed during a chemical reaction |
| coefficient | a number in front of a chemical formula in an equation that indicates how many molecules or atoms of each reactant and product are involved in a reaction |
| concentration | the amount of one material dissolved in a given amount of another material |
| chemical property | a characteristic that is observed when a substance interacts with another substance |
| chemical bond | the force that holds atoms together |
| decomposition | a chemical reaction that breaks down compounds into simpler products |
| electron dot diagram | a representation of the number of valence electrons in an atom,using dots placed around the symbol of an element |
| electron | a tiny,negatively charged,high-energy particle that moves in the space outside the nucleus of an atom |
| element | a substance composed of a single kind of atom. Elements cannot be broken down into othersubstances by chemical or physical means |
| formula | a combination of symbols that shows the ratio of elements in a compound |
| inhibitor | a material that decreases the rate of a reaction |
| metalloid | an element that has some of the characteristics of metals and some of the characteristics of nonmetals |
| molecule | a combination of two or more atoms that are bonded together; the smallest unit of most compounds |
| neutron | a small particle in the nucleus of the atom, with no electrical charge |
| nonmetal | an element that lacks most of the properties of metal |
| nucleus | (1)the control center of a cell that directs the cell's activities,contains the chemical instructions that direct all the cell's activities and determine the cell's characteristics.(2) the central core of an atom,containing protons and neutrons |
| period | a horizontal row of elements in the periodic table |
| periodic table | an arrangement of the elements in order of atomic number,in which elements with similar properties are grouped in columns |
| physical property | a characteristic of a substance that can be observed without changing the substance into something else |
| precipitate | a solid forms from a solution during a chemical reaction |
| product | a substance formed as a result of a chemical reaction |
| proton | a small, positively charged particle in the nucleus of an atom |
| reactant | a substance that enters into a chemical reaction |
| replacement reaction | a reaction in which one element replaces another in a compound;or when two elements in different compounds trade places |
| subscript | a number in a chemical formula that tells the number of atoms in a molecule or the ratio of elements in a compound;written lower ans smaller than the symbol |
| symbol | a one or two letter set og characters that is used to identify an element |
| synthesis | a chemical reaction in which two or more simple substances combine to form a new, more complex substance |
| valence electron | the electrons that are farthest away from the nucleus of an atom and are involved in chemical reactions |
| group | elements in the same verticle column of the periodic table; also called family |
| enzyme | (1)a protein that speeds up chemical reactions in the bodies of living things (2)A biological catalyst that lowers the activation energy of reactions in cells |
| exothermic reaction | a chemical reaction that releases energy in the form of heat |
| endothermic reaction | a chemical reaction that absorbs heat |
