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Unit 3 6th Grade
Elements, Compounds, and Reactions
Term | Definition |
---|---|
electron | a particle with a negative electrical charge |
nucleus | the center of an atom which contains most of the atom's mass |
proton | a positively charged particle inside an atom's nucleus |
neutron | a particle that is found in the nucleus of an atom and has no electrical charge |
electron cloud | an area where electrons arranged in energy levels travel around an atom's nucleus |
element | a pure substance that cannot be broken down into a simpler substance |
atomic number | the number of protons in an atom of an element |
isotope | one of two or more atoms of an element having the same number of protons but a different number of neutrons |
average atomic mass | the average mass of the atoms of an element |
periodic table | a chart that shows the elements in order of increasing atomic number |
compound | a substance formed by the chemical combination of two or more elements |
ion | an atom that is positively or negatively charged because it has gained or lost electrons |
ionic bond | an attraction that holds oppositely charged ions close together |
covalent bond | a chemical bond that forms when atoms share electrons |
exothermic reaction | a chemical reaction that releases energy |
endothermic reaction | a chemical reaction that absorbs energy |
rate of reaction | the measure of hos fast a chemical reaction occurs |
catalyst | a substance that speeds up a chemical reaction but is not used up itself or permanently changed |