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30 Cards in this Set
- Front
- Back
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What does Avagadro's number tell you?
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The number of particles in one mole of a substance. (6.02E23)
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What is the empirical formula of a compound?
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The empirical formula tells you the simplest ratio of the atoms involved.
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How did Mendeleev arrange his version of the periodic table?
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In order of relative atomic mass, swapping elements whose chemical properties did not match and leaving gaps for elements that he predicted would be discovered.
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What is periodicity?
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Periodicity is exhibited if there is a regular pattern in a property as you go across a period and this pattern is repeated in other periods.
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Give three examples of periodicty.
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1. Melting and boiling point.
2. Electrical conductivity. 3. Ionisation enthalpies. |
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Define first ionisation enthalpy.
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The energy required to remove an electron from one mole of atoms of the element in the gaseous state. (in Kj/mol)
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Give the general equation for the first three ionisation enthalpies.
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1. X(g) --> X+(g) + e-
2. X+(g) --> X2+(g)+ + e- 3. X2+(g) --> X3+(g)+ + e- |
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Define an isotope.
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Atoms of the same element, that have the same atomic number, but a different mass number. ie different numbers of neutrons.
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What does the mass spectrometer tell us?
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It can tell us about the relative isotopic masses and the relative abundance of these isoptopes. (see picture in revision guide)
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What is a mass spectrum?
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A mass spectrum is a graph that shows the intensity of different isotopes of the same element.
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What makes atoms unstable?
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Some isotopes have unstable nuclei (ie too many protons or neutrons), resulting in it being radioactive.
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What are the three types of radiation?
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Alpha
Beta and Gamma |
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What is alpha radiation?
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A stream of helium nuclei, that can be stopped by paper or skin.
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What is beta radiation?
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A stream of electrons that can be stopped by aluminium foil.
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What is gamma radiation?
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An electromagnetic radiation having no effect on the mass/charge of the nucleus. It can be reduced by thick lead sheets.
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Define an isotope's half life.
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The half life is the time it takes for half the nulcei in a sample of a radioactive isotope to decay.
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What properties should a radioactive tracer have?
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It should usually emit beta radiation as this is not stopped by skin. It's half life should not be too long or it may harm the patient; or too short as it may then not be able to be detected.
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What is nuclear fusion?
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The joining of two nulcei to form a heavier nucleus. Needs high temperatures to overcome the repulsion between the nuclei.
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When does nuclear fusion occur?
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During star formation.
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What is an energy level?
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A fixed energy level that electrons can occupy. Electrons always reside in SPECIFIC energy levels.
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What are absoption spectra?
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When an electron absorbs a specific amount of energy it becomes excited and can move up an energy level. The frequency of light that it absobs is seen as a black line on a coloured background.
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What are emission specta?
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When the electron has moved up an energy level it will then move back down, releasing the same frequency of light that it absobed. Seen as a coloured line on a black bacground.
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What does an emission or absoption spectrum tell you?
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Every element has a unique absoption or emission spectrum, meaning it can be identified by it.
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What bond do metals and metals form?
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Metallic bonds: positive metal ions are arranged in a regular lattice in a sea of the delocalised electrons that come from the outer shell of the metal.
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What bond do metals and non-metals form?
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Ionic bonds: the metal atom transfers electrons to the non-metal so that all atoms have a full outer shell. The opposite charges attract (electrostatic attraction). They are held together in a giant ionic lattice.
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What bonds form between non-metals and non-metals?
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Covalent bonds: the two atoms share a pair (or more) of electrons. Represented by dot and cross diagrams.
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What is a dative covalent bond?
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This is where both of the bonding electrons come from the same atom.
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What bond angle do four groups of electrons result in?
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109 degrees
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What bond angle do three groups of electrons result in?
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120 degrees
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What bond angle do two groups of electrons result in?
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180 degrees
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