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22 Cards in this Set
- Front
- Back
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What is an element? |
A substance that cannot be broken down further into simpler substances through chemical reactions. |
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State Dalton's ideas on atoms |
- matter is made up of tiny indivisible particles called atoms -atoms can neither be destroyed nor created -atoms of the same element are alike in every way -atoms of different elements are different -atoms can combine together to form molecules |
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What is an atom |
simplest unit of an element |
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Difference between molecule and compund |
Molecule : two or more atoms join together chemically Compound: a molecule that contains different elements |
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Explain Thomson's discovery on the existence of electrons. |
when high voltage applied across two electrodes, a stream of negatively charged particles produced. he came up with plum pudding model - electrons scattered in positively charged spongelike substance. |
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what was Rutherford's experiment and discovery? |
Experiment: fire alpha particles at gold foil Discovery: Most when straight through ( atom largely spaced), some were largely deflected ( repelled by large + nucleus) , small number of particles bounced back( nucleus very small) |
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Relative mass and charge of neutrons, protons and electrons |
charge : 0, +1, -1 mass : 1, 1, 0.0005 |
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What prevents electrons from leaving the atoms |
Electrostatic force of attraction between oppositely charged sub atomic particles. |
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why have neutrally charged neutrons in nucleus? |
crucial for stability, or else protons repel each other and fall apart |
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Define isotopes |
atoms of the same element with different mass numbers |
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calculating average relative mass |
total mass/ number of atoms |
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Define the relative atomic mass of an element |
the average mass of an atom of the element taking into account all of its isotopes, their relative abundance compared to one atom of carbon 12 |
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What is the x and y axis of a mass spectrum ? |
x axis : mass/charge ration y axis: % abundance |
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How does wavelength and frequency vary in the electromagnetic spectrum? |
wavelength decreases while frequency incresess, energy increases as well |
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which colour has the shortest and longest wavelength |
violet, red |
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Define frequency and wavelength |
Frequency- the number of waves that past a point at one particular point wavelength- the distance between two successive crest ( throughs) |
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What is an absorption spectrum ? |
absorption spectrum has some missing colour lines. these are the energies that the atoms have absorbed to move from lower energy level to higher level |
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What is an emission line spectrum? |
The colours present in this spectrum are the ones that were missing in the absorption spectrum. The light emitted was when atoms fall from high energy level to low energy level. |
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state planck's constant |
6.63 * 10^-34 js |
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explain convergence in an atom |
Higher energy levels are closer together |
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Define Lyman, Balmer and Paschen series |
Lyman : when electrons fall to n =1 (uv) Balmer: when electrons fall to n=2 (light) Paschen : when electrons fall to n=3 ( ir) |
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what is an atomic orbital ? |
a region around the nucleus where there is 90% chance for an electron to be found. |
