Molecular Shape Flashcards
Tetrahedral
4 areas of electron density
4 bond pairs
0 lone pairs
Bond angle: 109.5°
Trigonal planar
3 areas of electron density
3 bond pairs
0 lone pairs
Bond angle: 120°
Pyramidal
4 areas of electron density
3 bond pairs
1 lone pair
Bond angle: 107°
Bent
4 areas of electron density
2 bond pairs
2 lone pairs
Bond angle: 104.5°
Octahedral
6 areas of electron density
6 bond pairs
0 lone pairs
Bond angles: 90°
What is electronegativity
- The attraction of a bonded atom for the pair of electrons in a covalent bond.
- EN increase from left to right on the periodic table
Polar and Non polar molecules
Polar:
-when the bonded atoms are different or have different EN values resulting in a polar covalent bond
Non polar
-when the bonded atoms are the same or have similar EN values resulting in a pure covalent bond
Dipoles
Dipole- the separation of opposite charges
A dipole on a polar covalent bond is a permanent dipole as it doesn’t change
Forces between molecules
Covalent bonds- strong and hold the atoms in a molecule together
Intermolecular forces- weak interactions between dipoles of different molecules
Intermolecular forces
Induced dipole dipole interactions (london forces)
Permanent dipole dipole interactions
Hydrogen bonding
Induced dipole dipole interactions (london forces)
Weak intermolecular forces that exist between all molecules (polar and non polar)
Hydrogen bonds
A type of permanent dipole dipole interaction found between molecules containing:
- an EN atom with a lone pair of electrons (e.g. Oxygen, fluorine, nitrogen)
- a hydrogen atom paired to a EN atom (e.g. H–N, H–F, H–O)
- Always partially positive
- Acts between a lone pair of electrons on an EN atom in a molecule and a hydrogen atom in a different molecule
- Strongest type of intermolecular force
