CHEMISTRY TOPIC 1: THE ATOM REVIEW

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Rutherford Experiment:
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Bombarded gold foil with alpha particles. Showed atoms were mostly empty space with small, dense positively charged nucleus.
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Bohr Model:
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Small, dense, positively charged nucleus surrounded by electrons in circular orbits.
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Wave-Mechanical Model (Modern Atomic Theory)
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Small, dense, nucleus positively charged nucleus surrounded by electrons moving in \”electron cloud\”. \”Orbitals\” are areas where an electron with a certain amount of energy is most likely to be found.
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* Each atom is made of a……*
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positively charged nucleus with one or more orbiting, negatively charged electrons.
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* Protons and neutrons are found in the *
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nucleus
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Protons have a ………..charge
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positive
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neutrons have………. charge
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no
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electrons have a………….charge
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negative
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The mass of a proton is
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1 amu.
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The mass of a neutron is
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1 amu
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The mass of an electron is almost
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1/1836 amu
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When all electrons are at their lowest possible energy, it is called the
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ground state
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When the electron gains a specific amount of energy, it moves to a higher orbital and is in the
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\”excited state\”.
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When an electron returns from a higher energy state to a lower energy state, it ……
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emits a specific amount of energy usually in the form of light. This can be used to identify an element (bright line spectrum). The instrument used to see the bright line spectrum is called a spectroscope.
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The outermost electrons are called valence electrons. These affect the…………………………
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chemical properties of the element.
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Atoms of the same element all contain the same number
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of protons
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Isotopes are atoms with…………..
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equal numbers of protons but different numbers of neutrons. *different atomic masses (protons + neutrons).*
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The average atomic mass of an element is the
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weighted average of its naturally occurring isotopes.
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JJ Thomsons model
JJ Thomsons model
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Used cathode ray tube Negative electrons (in mixture ) Plum pudding model !!! -uniform density
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When an atom is neutral …
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Protons = electrons
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Mass number
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Protons +neutrons
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Mass number and atomic #
Mass number and atomic #
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Atomic number
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# of Protons = # of electrons
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Isotopes
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Same atomic number but different mass number – different number of neutrons
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Calculating atomic mass
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% abundance x mass for each isotope (add all) 1 change percent to a decimal 2 multiply decimals with amu ( correct sigs 3 add all masses together ( sigs
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Ion
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~ gain electrons = negative ion ~lose electrons = positive ion

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