shapes of molecules Flashcards
what are bonding and lone pairs
bonding–> shared electrons
lone–> unshared
both exist as charged clouds
what is the electron pair repulsion theory
-explains shapes of molecules and polyatomic ions
-electron pairs surrounding central atom determines the shape of the molecule or ion
-arrangement of electron pairs minimises repulsion and holds bonded atoms in definite shape
-different numbers of electron pairs result in diff shapes
what are the relative repulsions between electron pairs from weakest to strongest
- BP+BP
- BP+LP
-LP+LP
shape and angle of 2BP + 0LP
linear
180
shape and angle of 2BP + 1LP
trigonal planar non linear
117.5
shape and angle of 3BP + 0LP
trigonal planar
120
shape and angle of 4BP + 0LP
tetrahedral
109.5
shape and angle of 3BP +1LP
trigonal pyramidal
107
shape and angle of 2BP + 2LP
trigonal planar non linear
104.5
shape and angle of 5BP + 0LP
trigonal bipyramidal
trigonal base with bond angle - 120 and other 2 bonding between them at top and bottom are at an angle of 90
shape and angle of 6BP and 0 LP
octahedral
90
what is electronegativity
the attraction of a bonded atom for the pair of electrons in a covalent bond
how is electronegativity measured
- pauling scale
flourine has highest electronegativity
what factors effect electronegativity
nuclear charge–> greater positive charge–> greater attraction to shared electrons–> greater electronegativity
atomic radius–> smaller atomic radius–> smaller number of shells–> smaller distance between nucleus and shared electrons–> greater attraction–> greater electronegativity
sheilding–> smaller number of shells–> less repulsion from inner shell electrons–> greater attraction towards shared electrons–> greater electronegativity
what are trends in electronegativity across a period
-increases
- nuclear charge increases
- atomic radius decreases
- sheilding remains the same
what are polar bonds
- the bonded electron pair is shared unequally between bonded atoms
- bonded atoms have different electronegativity values
what are non polar bonds
- electron pair shared equally between bonded atoms
- when bonded atoms r the same or have similar electronegativity
- if bonded atoms are of the same element its a pure covalent bond
what happeneds when the more electronegative atom gains control of the electrons due to very strong attraction making the bond ionic rather than covalent
it becomes an ionic bond
what is a dipole
seperation of opposite charges
what are polar molecules
- molecule that have permanent dipoles
- depends on shape
-dipoles point in roughly the same direction
