Chemistry Unit #4 Terms: Atomic Theory

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Decomposition Reaction

Back 1

when a complex substance breaks down into its simple parts. One reactant yields 2 or more products

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Synthesis Reaction

Back 2

when two or more simple substances combine to form a more complex substance. Two or more reactants yielding one product

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Element

Back 3

a pure chemical substance consisting of one type of atom distinguished by its atomic number

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Compound

Back 4

pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions

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Calcination

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thermal treatment process applied to metals and other solid materials in order to bring about a thermal decomposition; normally takes place at temperatures below the melting point of the product

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Law of Constant Proportion

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a chemical compound always contains exactly the same proportion of elements by mass

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Law of Multiple Proportions

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when chemical elements combine, they do so in a ratio of small whole numbers

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John Dalton

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conjured up the idea we now call "atomic theory"

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4 Parts to Atomic Theory

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1) all elements composed of tiny indivisible particles
2) atoms of the same element are identical and are different from those of another element
3) atoms can mix or chemically react in simple whole number ratios
4) in a chemical reaction, atoms are joined, rearranged, or separated. individual atoms however never change into atoms of another element

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Atom

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smallest particle of an element that retains the properties of that element

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JJ Thomsen

Back 11

discovered the electron and isotopes; "Plum Pudding" model

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Cathode Ray Tube Experiment

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electrons move from negative side to positive side; they must have mass because they move the pinwheel; electrons are negatively charged

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Electron

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Mass: 1/2000 AMU
Charge: -1

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"Plum Pudding" Model

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depicted the atom as having a sort of "energy field" sprinkled with negatively charged particles (electrons) with a positively charged core (protons/neutrons in nucleus); JJ Thomsen

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Ernst Rutherford

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disproved the "Plum Pudding" model for the atom; also performed the gold foil experiment to reach his conclusions

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Gold Foil Experiment

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the majority of the alpha particles would pass through the atoms, signifying that there was a fair amount of empty space; however every once in a while the alpha particles would seem to bounce off of something this, Rutherford concluded, must be the positively charged nucleus

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Nucleus

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the positively charged portion of the atom; contains protons (+) and neutrons (no charge); solid and static

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Proton

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Mass: 1 AMU (one hydrogen atom)
Charge: +1

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Neutron

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resides in the nucleus with the protons; has no charge

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Atomic Number

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number of protons in nucleus; defines atoms; change the atomic number (# of protons) and you have a different element

Front 21

JJ Thomsen

Back 21

discovered the electron and isotopes; "Plum Pudding" model

Front 22

Cathode Ray Tube Experiment

Back 22

electrons move from negative side to positive side; they must have mass because they move the pinwheel; electrons are negatively charged

Front 23

Electron

Back 23

Mass: 1/2000 AMU
Charge: -1

Front 24

"Plum Pudding" Model

Back 24

depicted the atom as having a sort of "energy field" sprinkled with negatively charged particles (electrons) with a positively charged core (protons/neutrons in nucleus); JJ Thomsen

Front 25

Ernst Rutherford

Back 25

disproved the "Plum Pudding" model for the atom; also performed the gold foil experiment to reach his conclusions

Front 26

Gold Foil Experiment

Back 26

the majority of the alpha particles would pass through the atoms, signifying that there was a fair amount of empty space; however every once in a while the alpha particles would seem to bounce off of something this, Rutherford concluded, must be the positively charged nucleus

Front 27

Nucleus

Back 27

the positively charged portion of the atom; contains protons (+) and neutrons (no charge); solid and static

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Proton

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Mass: 1 AMU (one hydrogen atom)
Charge: +1

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Neutron

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resides in the nucleus with the protons; has no charge

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Atomic Number

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number of protons in nucleus; defines atoms; change the atomic number (# of protons) and you have a different element

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Mass Number

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number of neutrons and protons in the nucleus

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AMU

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the measurement used when measuring the mass of atoms; 1 AMU is equivalent to one Hydrogen atom

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Isotopes

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forms of a certain element with a different mass number which means that their are more/less neutrons than usual

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Atomic Mass

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the total mass of neutrons and protons in AMUs

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Weighted Average

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where instead of each of the data points contributing equally to the final average, some data points contribute more than others; weighted average of the atomic masses of all the atoms of a chemical element found in a particular sample, weighted by isotopic abundance

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Metal

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good conductor; forms cations and ionic bonds with non-metals; form salts when reacted with non-metals

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Non-Metals

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low densities; low electronegativity (ability of an atom to attract electrons to itself); form salts when reacted with metals

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Ionic Compounds

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a chemical compound where ions are held together in a box structure by ionic bonds; the positively charged portion consists of metal cations and the negatively charged portion is an anion or polyatomic ion. Ions in ionic compounds are held together by the electrostatic force between oppositely charged bodies; have high melting and boiling point, and are hard and brittle

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Formula Unit

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shows the kinds and numbers of atoms in the smallest representative unit of a substance

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Molecule

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a group of at least two atoms in a definite arrangement held together by covalent chemical bonds

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Molecular Compound

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a compound made of 2 or more nonmetal elements

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Salts

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a compound formed between a metal and non-metal

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Anion

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an ion with more electrons than protons, giving it a net negative charge

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Cation

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an ion with fewer electrons than protons, giving it a positive charge

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Polyatomic Ion

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a charged ion composed of two or more atoms covalently bonded in the formation of salts