Topic 3: Bonding Flashcards
(30 cards)
Ionic
Large differences in electronegativity, between metals and non metals. Electrostatic att’n b/w charged ions.
Covalent
Small differences in electronegativity, between non metals. Shared pair of electrons.
Metallic
Between metals. Electrostatic att’n b/w ions and delocalised e-
Ionic Structure
Giant ionic lattice
Ionic Properties
- High melting point … strong att’n between oppositely charged ions means hard to overcome, higher the charge, higher the att’n, higher the melting point
- Electrical conductor when molten/ in sol’n… Ions can dissociate and so are free to move and can carry charge.
Covalent Properties (Diamond and Sillicon)
- High melting point/ hard… lots of strong covalent bonds, hard to overcome.
Covalent Properties (Graphite)
- High melting point (same reason as diamond)
- Slippery… weak v.d.w. between layers so can slide
- Conducts electricity… single delocalised electron can carry charge
Covalent Properties (Iodine)
- Low boiling point… weak v.d.w. forced between molecules, little energy required to overcome.
Metalic Properties
- High melting point… strong att’n between delocalised electrons and cations, greater the charge the more electrons, the stronger the att’n.
- Electrical conductors… delocalised electrons can move throughout structure and carry charge
- Malleable/ ductile… layers of ions can slide also means brittle
Malleable def
The ability of a something to be deformed or shaped without breaking
Ductile
The ability of a something to be stretched or drawn into wire form without breaking
Dative Bonding
A covalent bond in which both electrons come from the same atom (a lone pair).
2 Bonding pairs
Linear, 180°, O=C=O
3 Bonding pairs
Trigonal Planar, 120 °, looks like flat triangle with 3 bonds, BF3
4 Bonding pairs
Tetrahedral, 109.5 ° 3D shape you know it, CH4
5 Bonding pairs
Trigonal Bipyramid, 120° and 90° straight up, straight down, straight left, right up to the back, right down to the front, PCl5
6 Bonding pairs
Octahedral, 90°, straight up, straight down, sides up, sides down, SF6
3 Bonding pairs, 1 Lone pair
Trigonal Pyramid, 107°, tetrahedral without the top atom, NH3
2 Bonding pairs, 2 Lone pairs
Angular, 104.5°, V shapes, H20
Intermolecular Forces
The attractive and repulsive forces that arise between the molecules of a substance.
Van der Waals forces
- Weakest IMF
- Exist in all molecules or atoms
- The electron charge cloud constantly moving (electron density is uneven)
- The electron charge cloud can be more on one side of the atom or molecule than the other
- This causes a temporary dipole to arise
- This induce a dipole on neighbouring molecules
- When this happens, the δ+ end of the dipole in one molecule and the δ- end of the dipole in a neighbouring molecule are attracted towards each other
- Because the electron clouds are moving constantly, the dipoles are only temporary
Strength of V.d.w difference in different molecules
The larger the molecule/atom, the more electrons so greater electrostatic att’n, stronger v.d.w forces.
Saturated/ unsaturated fats and v.d.w
Saturated fats have stronger v.d.w as they have straight chains so can fit together and form more v.d.w. Opposite for unsaturated as have a kink in chain.
Dipole- dipole forces
- Occurs in permanently polar molecules
- Uneven distribution of electron cloud
- This means there is a delta positive and delta negative region to the molecule
- Interacts with other molecules, electrostatic att’n to opposite delta charge
- The greater the polarity of a bond or molecule, the stronger the permanent dipole-dipole interactions.
