3.1 - 3.7 Bonding Flashcards
What is an ionic bond?
The electrostatic attraction between oppositely charged ions
Positive ion
Cation
Negative ion
Anion
What is a covalent bond?
A shared pair of electrons. The electron pair is attracted to both nuclei so resist separation.
What is a co-ordinate bond?
A covalent bond where both electrons in the shared pair originate from the same atom
What is metallic bonding?
The attraction between positive metal atoms and the surrounding delocalised sea of electrons
What is electronegativity?
The power of an atom to attract the pair of electrons in a covalent bond
Nuclear charge up = electronegativity ?
Electronegativity up
Atomic radius up = shielding ? = electronegativity ?
Shielding up = electronegativity down
What is used to measure electronegativity?
The Pauling scale
What happens to electronegativity across a period?
- Increases
- Same no. of energy levels BUT
- Increasing no. of protons/nuclear charge
- Decreasing atomic radius
What happens to electronegativity up a group?
- Increases
- Fewer energy level in use
- Less shielding
- Decreasing atomic radius
What is a polar molecule?
One in which the electron density across the whole molecule is unevenly distributed
What is a permanent dipole?
When one side of the molecule is permanently more negative, happens when a molecule is not symmetrical
What are the 3 main types of inter-molecular forces?
- Dipole-dipole interactions
- Hydrogen bonding
- Van der Waal’s forces
What are dipole-dipole interactions?
- Attractive forces between polar molecules
- Whatever their starting position, molecules will ‘flip’ to attract
What are hydrogen bonds?
- Not a bond, an inter-molecular force
- Only takes place when H bonded to O, F or N with at least one lone pair
What are Van der Waal’s forces?
- Also known as temporary dipole-induced dipole interactions
- Caused by the movement of electrons so the more electrons there are the stronger the force
- Exist between all molecules at all times, in addition to any other forces
List the three main inter-molecular forces from weakest to strongest
- Van der Waal’s
- Dipole-dipole
- Hydrogen bonding
Describe the particles in a solid
Regular, close, vibrate about a fixed position
Describe the particles in a liquid
Random, close, can move past each other
Describe the particles in a gas
Far apart, rapid and random motion