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        | Branch of science that considers the composition of matter and how this composition changes |  | 
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        | Anything that has weight and takes up space; solids, liquids, gases |  | 
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        | Mass is the amount of space something takes up; where as weight is how heavy something is |  | 
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        | All matter composed of substances; common materials such as iron, copper, silver, gold, aluminum, carbon, hydrogen, and oxygen |  | 
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        | The smallest complete units of elements |  | 
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        | A center portion called a nucleus and one or more electrons that constantly move around the nucleus |  | 
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        | Large positive charged particles that form part of a nucleus |  | 
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        | Large neutral charged particles that form part of a nucleus |  | 
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        | Very small negative charged particles that surround the nucleus |  | 
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        | The number of protons in the atom |  | 
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        | The number of protons and neutrons in an atom |  | 
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        | Atoms of an element with different atomic weight |  | 
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        | Unstable isotopes are called radioactive because... |  | Definition 
 
        | The energy or atomic fragments they give off are referred to as radiation |  | 
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        | Three forms of radiation are called |  | Definition 
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        | Alpha radiation consists of... |  | Definition 
 
        | Particles from atomic nuclei, each of which includes two protons and two neutrons that travel slowly and can weakly penetrate matter |  | 
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        | Beta radiation consists of... |  | Definition 
 
        | Very small particles (electrons) that travel rapidly and penetrate matter deep |  | 
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        | The highest level of penetration; similar to x-ray radiation |  | 
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        | The time it takes for an isotope to lose one half of it radioactivity |  | 
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        | When electrons occupy more than one area of space around a nucleus. First shell consists of two electrons and the following two hold 8 electrons |  | 
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        | Atoms that gain or lose electrons and become electrically charged |  | 
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        | When two atoms share electons |  | 
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        | When two oppositely charged ions combine |  | 
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        | When a covalent bond doesn't share the electrons equally |  | 
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        | Weak bond between a hydrogen atom and an atom of oxygen or nitrogen between molecules or different regions of a very large molecule |  | 
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        | When two or more atoms of the same element bond together |  | 
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        | When atoms of different elements bond, they form molecules called compounds |  | 
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        | Represents the numbers and types of atoms in a molecule - The formula for water is H2O |  | 
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        | Three dimensional models of structural formulas |  | 
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        | Form or break down bonds between atoms, ions, or molecules, generating new chemical combinations |  | 
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        | When two or more atoms bond to form a more complex structure |  | 
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        | If the bonds within a reactant molecule break down into simpler molecules, atoms, and ions form |  | 
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        | When two bonds are broken down and shared forming two new bonds |  | 
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        | When two bonds are broken down and exchange molecules (able to reverse this) |  | 
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        | Chemical that increases the rate of a chemical reaction but is not altered by it |  | 
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        | Substances that release ions in water |  | 
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        | Electrolytes that release hydrogen ions (H+) in water |  | 
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        | Electrolytes that release ions that bond with hydrogen ions |  | 
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        | Measures hydrogen ion concentration |  | 
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        | Contains more hydrogen ions and is less than 7.0 |  | 
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        | Contains less hydrogen ions and is greater than 7.0 |  | 
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        | Substance that can react with a strong acid or base to form a weaker acid or base and thus resist a change in pH |  | 
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        | Chemicals that include both carbon and hydrogen atoms; do not release ions, therefore nonelectrolytes |  | 
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        | Chemicals that release ions; therefore, electrolytes (Oxygen, carbon dioxide, water, and salt) |  | 
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        | Substance dissolved in a liquid |  | 
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        | Carbon atoms are bond to as many hydrogen atoms as possible |  | 
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        | many double bond carbon atoms |  | 
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        | Differentiates one amino acid from the next |  | 
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        | Form genes and take part in protein synthesis; RNA and DNA |  | 
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