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general chemistry - chapter 8, pairs, halogens never make multiple bonds -…
general chemistry - chapter 8
chemical bonds
ionic bond
typically the bond between a metal and a non-metal where electrons are transferred to the atom with a higher EN to complete an octet
polar covalent
EN differs by less than two units
when electrons are unequally shared between two atoms but are not completely transferred
one atom may have a higher EN than the other, so despite the electrons being shared, they will be more attracted to the higher EN
difference between polar covalent and covalent : covalent bonds are typically shared between two atoms of the same element or of similar EN while polar covalent bonds are not
covalent
involves sharing pair(s) of electrons between atoms rather than transferring
done with two atoms with elements of the same or similar EN and the electron is shared equally
electronegativity (EN)
the ability of an atom in a molecule to attract shared electrons to itself
periodic table : highest EN is at the top right and lowest EN is at the bottom left
dipole moment
having polar bonds doesn't necessarily mean they have a dipole moment
specifically when the individual polarities are arranged in such a way that they cancel each other out (like vectors)
a molecule that has a center of positive and a center of negative charge
Lewis structure
a chemical symbol to represent the nucleus and core electrons of an atom, together with the dots placed around the symbol to represent the valence electrons
when drawing the molecule with Lewis structure, the element with the lowest EN is in the center and is connected to the terminals
resonance
resonance structure : when there is more than one possible Lewis structure for a molecule where it's only different in the position of the electrons
resonance hybrid : if they have equivalent structures, then the actual molecule is a combination of the resonance forms
rules
formal charges
for each element : = (nbr of e- in free atom) - (nbr of lone pair e- + ½ bond pair e-)
octet rule exceptions
C, N, O, F always obey the octet rule
certain elements can have an incomplete octet (< 8 valence electrons)
the central atom can have an expanded octet (10/12 valence electrons)
pairs
covalent bonds
lone pairs : electrons not shared by atoms but belong to a particular atom
halogens never make multiple bonds
bonding pairs : electrons shared by atoms
single covalent bond : two atoms share two electrons
exception : H-only duet
double covalent bond : two atoms share four electrons
triple covalent bond : two atoms share six electrons