Shapes Of Molecules Flashcards
Effect of lone pair in shape of molecule
Bond angle decreases by 2.5 degrees per lone pair
Tetrahedral
4 bonded pairs
109.5 degree Bond angle
Pyramidal
3 bonded pairs
1 lone pair
107 degree Bond angle
Trigonal planar
No lone pairs
120 angle
3 electron pairs
Linear
2 electron pairs
180 angle
Octahedral
6 electron pairs
90 degree
Electronegativity
An atoms ability to attract electron pair in a covalent Bond
Decreased down groups and increases across periods
Symmetrical polar bonds
Cancel each other out so no overall dipole and is non-polar
Dipole
Difference caused by shift in electron density in bond
Induced dipole dipole
Electrons in charge cloud, more likely to be more to one side than another so have temporary dipole
Temporary dipole can cause another temporary dipole in opposite direction so attracted
Larger molecules have larger electron cloud so stronger induced dipole
Weak induced dipole keep I2 in molecular lattice
Permanent dipole dipole
Slight positives and negative charges cause weak electrostatic attraction between molecules
Hydrogen bonding
Only happen when hydrogen covalently comes to fluorine, nitrogen or oxygen
Hydrogen has high charge density and other are very electronegative
Bond polarised that weak bond forms between hydrogen and lone pair of electrons
Effect of more electrons
Stronger induced dipole interactions
Polar bond
In covalent bonds between 2 atoms of different electronegativites bonding electrons pulled to more electronegative atom
Difference in electronegativity cause permanent dipole
Simple covalent Molecules behaviours
Low melting and boiling points
Polar molecules soluble in water
Don’t conduct electricity
