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Understanding chem, Chem Review - Coggle Diagram
Understanding chem
Resonance
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You will not understand how, but each atom has a satisfied octet in these resonance structures hybrids
Resonance structure hybrids are stable because they disperse the negative ion charge over a large space, which for some reason means that it is more stable
Spreading negative charge over a larger region reduces the concentration of electron density → reduces electron–electron repulsion → lowers the molecule’s energy → makes it more stable.
Resonance structures
These do not exist, and are structures that have the atoms in the same SPOTS, but different electrons organized around (i.e. lone pairs vs bonds etc.)
Lone pairs: if a lone pair can move into an adjacent π system to give a valid resonance structure, it participates in resonance and typically occupies a p orbital. Otherwise, it is localized.
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For now, the movement of 2 electrons creates the adjacent p orbitals
Rules
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Must have orbital overlap for resonance (this means that the p orbitals must be oriented such that they can overlap)
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For nonequivalent structures, the more stable structure contributes to the resonance structure more.
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The more covalent bonds the structure has, the more stable it is
Structures with atoms with full valence shells are more stable than ones without full valence shells
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the molecule with teh correct charge on the correct atom contributes more (most elecneg at negative, least electroneg at positive)
Chem Review
Periodic Table
Groups
There are 18 groups
Starting with Alkali metals, then alkaline earth metals, then transition metals, then nonmetals (halogens, nobel gases), lactinides and athanaides.
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Blocks on the periodic table indicate the electron congifuration of the elements (i.e. first two columns have the highest energy orbital being the s orbital, next is d, next is p)
Isotope notation
Chemical symbol, above is mass number, z is atomic number, a-z is number of neutrons, and charge is = protons - electrons
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Electronegatviity
Increases as you go bottom to top, because shells get fewer, less shielding, more attraction to outermost shells and more attraction to electrns.
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Dipole, this is a different in electronegativities, have a dipole, have bond polarity!
Quantum numbers
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Spin quantum number (ms)
tells the spin of the electrons, can either be -1/2 or 1/2 in an orbital
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Carbon is special:
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Compare:
C: 4 bonds → octet, FC = 0
N: 3 bonds + 1 lone pair → octet, FC = 0
O: 2 bonds + 2 lone pairs → octet, FC = 0
So carbon's neutral, octet-satisfied state happens to involve more covalent bonds than N or O.
Bonding
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Ionic
This is the loss or gain of electron, and bond that forms due to the different charges being attracted to one another.
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Rotation & planar
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Planar if you have sp or sp2 hybridization because the double bond holds it in place, and all teh other orbitals must be in the same plane, which means that they are 90* waay from p and thus in the same plane as the other side
Bond strength
The more the electron density overlap, the stronger the bond because the electrons are closer to either nucleus, the harder it is to break the bond and the closer the atoms are in the bond.
So, bonding between two atoms, if you increase an atoms valence shell's principle quantum number, then you get weaker bonds
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Hybridization: essentially, hyrbidize so that all sigma bonds are equal. Promotion gets you the right number of orbitals that can be part of bonding.
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Isomerization, when you add energy to promote an electron in a pi bond omlecular orbital to the antiboding, its not longer a bond, you can rotate to get a new isomer and then it forms the bond again.