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Dalton’s Theory:
- All matter consists of atoms
- All atoms of a given atom are identical (false, isotopes)
- The atoms of a given element are different from other elements and compounds
- Atoms can not be created, destroyed or broken into smaller pieces (false)
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Atomic Number:
Z
Is the number of protons in the atom.
Is on the bottom left corner.
For a neutral atom, number of protons = number of neutrons
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The Mass Number:
A
The mass of the atom is concentrated in the nucleus, which contains protons and neutrons.
Upper left corner of the atom
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Isotopes:
Same proton, different neutron number
Chemical properties are determined by number of electrons and are thus the same
Physical properties vary
-higher mass
-higher density
-higher melting and boiling points
-slower rate of diffusion
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Why are isotopes useful?
Treating different kinds of cancer
The sterilization of surgical instruments
Nuclear power
Crime detection
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Useful Isotopes:
Cobalt 60
Iodine 131
Iodine 125
carbon 12
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Relative Atomic Mass;
mass x relative abundance) of all isotopes/ 100
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Electron Arrangement
The Bohr model is the basis
An electron arrangement gives the number of electrons in each shell or orbit
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Main energy level,
- n, is called principal quantum number
- increases as we get further from the nucleus
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n
n=1 has an s orbital
n=2 has an s and a p orbital
n=3 has an s, p and a d orbital
n=4 has an s, p, d, f orbital
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Full Electron Configuration
Normal
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Condensed/ Abbreviated Electron Configuration
With a soygaz
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Orbital Diagram Representation
With the boxes
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Ionisation Energy
- Ionization energy is the energy required to remove one mol of electrons from one mol of atoms in the gaseous state.
- increases as more electrons are removed
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As the atom gets bigger and as we move down the periodic table
ionization energy decreases bc electrons further from the nucleus are easier to remove
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The size of the atom decreases from left to right (same number of shells, more protons)
), thus the ionization energy increases
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Shielding:
inner electrons will shield electrons in lower shells by repelling them . The greater the shielding effect, the lower the ionization energy. More electrons = less ionization energy
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Exceptions: ionisation
It’s easier to remove electrons from subshell p
Be has a higher ionization energy than B
It’s easier to remove electrons from a full orbital
N has a higher ionization energy than O
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Number of protons and number of electrons
are equal for all atoms of an element
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the most dangerous
Short wavelength, high frequency, high energy
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Speed of light: c =
distance between successive crests x frequency
weird h x v
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= E
Electromagnetic Radiation, Energy of Photon
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E= formuola
- Planck’s constant x frequency.
- (h x v)
- since v = c/ weird h
- E= h.c/distance between crests
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Absorption line spectrum:
- electron absorbs energy, goes to a higher energy level
- mostly colorful with black lines
- converges at high frequency
- represents electrons going up from n=2
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Emission line Spectrum:
- Electron loses or emits energy and goes down to a lower energy level (lines on black)
- represents electrons going from n=2 to higher energy levels
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Transitions to n=1
UV radiation (highest energy)
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Transitions to n=2
visible light
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Transitions to n=3
are infrared (lowest energy)
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rays from highest energy to lowest energy
Gamma rays, X rays, UV, visible light, infrared, microwaves, radio waves
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