Unit 10 - VSEPR models

linear (2)

steric number 2, 0 lone pairs, 180 angle, planar

trigonal planar

steric number 3, 0 lone pairs, 120 angle, planar

bent (<120)

steric number 3, 1 lone pair, <120 angle, planar

tetrahedral

steric number 4, 0 lone pairs, 109.5 angle, 3D

trigonal pyramidal

steric number 4, 1 lone pair, <109.5 angle, 3D

bent (<<109.5)

steric number 4, 2 lone pairs, <<109.5 angle, 3D

Ionic bond

ve-s are transferred, solids at room temp (mp/bp), electrolytes

Covalent bond

ve-s shared, no metal present

polar covalent bond

e-s are not shared equally, have dipole moment (arrow, partial negative and positive)

non-polar covalent bond

e-s shared equally

electronegativity (EN)

tendency of an atom to attract shared e-s to itself (FONCl most attractive)

EN increasing across periods (L-R)

increased nuclear charge, more protons in the nucleus to attract e-s

EN decreasing down groups (top-bottom)

e- shielding, added energy levels protect e-s from nuclear force

Lewis structures

model showing how covalent bonding occurs

Si and on elements

Lewis exception, take extra electrons than octet

B and Be

Lewis exception, fewer than 8 e-s within compounds

Isomers

2 different compounds with the same formula

molecular shape

determines function of a molecule

VSEPR theory

Valence shell electron pair repulsion, electron pairs (shared or lone) want to be as far away (bond angle) from each other as possible

lone pairs

repel more than shared pairs

steric site/number

shared pairs (bonds) plus lone pairs of center atom (multiple bonds viewed as single bonds)

trigonal bipyramid

steric number 5, 0 lone pairs, 90 axial+equitorial angles, 120 equitorial+equitorial angles,, 3D

seesaw

steric number 5, 1 lone pair, <90 axial+equitorial angles, <120 equitorial+equitorial angles, 3D

t-shape

steric number 5, 2 lone pairs, <<90 angle, planar

linear (5)

steric number 5, 3 lone pairs, 180 angle, planar

Octahedral

steric number 6, 0 lone pairs, 90 angle, 3D

square pyramid

steric number 6, 1 lone pair, <90 angle, 3D

square planar

steric number 6, 2 lone pairs, 90 angle, 3D