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Earth Science Vocab from our 9th grade Text Book.


a substance that cannot be changed , a substance that cannot be separated or broken down into simpler substances by chemical means


smallest particle of an element


control center of the cell


positively charged particle


no charge

Atomic Number

the number of protons in the nucleus of an atom

Mass Number

the sum of the number of neutrons and protons in an atomic nucleus


negatively charged particle

Energy Level

place in an atom where an electron is most likely to be found

Valence Electron

an electron in the outermost electron shell


atoms of the same element that have different masses

Atomic Mass

total mass of the protons and neutrons in an atom, measured in atomic mass units


the process by which an unstable nucleus emits one or more particles or energy in the form of electromagnetic radiation


(chemistry) a substance formed by chemical union of two or more elements or ingredients in definite proportion by weight

Chemical Bond

the attractive force that holds atoms or ions together

Covalent Bond

a bond formed when atoms share one or more pairs of electrons


two or more atoms held together by covalent bonds


atom that has a positive or negative charge

Ionic Bond

bond formed when one or more electrons are transferred from one atom to another

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