3.1.3 Bonding Flashcards
Name the 4 types of crystal structure.
- Simple molecular
- Ionic
- Metallic
- Macromolecular
Give examples of macromolecular crystal structures.
- Silicon dioxide
- Diamond
- Graphite
What is a covalent bond?
Shared pair of electrons between two non-metals
What is a dative covalent bond?
When both electrons in a covalent bond are donated from one atom
What is a metallic bond?
Strong electrostatic attraction between the positive metal ions and delocalised electrons
Why can metallic compounds conduct electricity?
- Sea of delocalised electrons and positive metal ions.
- Delocalised electrons are free to flow and carry charge
Why are metallic compounds malleable?
- Layers of positive metal ions able to slide over eachother
- Layers don’t repel because of delocalised electrons
What are the factors that affect the strength of metallic bonds?
- Metal charge on ion (determines number of delocalised electrons per ion)
- Ionic radius on cation
(nuclear charge + shielding)
What is an ionic bond?
Strong electrostatic attraction between oppositely chagred ions.
Why can ionic compounds conduct electricity when molten/liquid state and not as a solid?
- Ions are free to move and carry charge when molten/liquid
- When solid, ions not free to move and carry charge
Why are ionic compounds hard and brittle?
- When layers slide over eachother the like charged ions repel eachother
- Layers repel and the structure breaks
What does the strength of an ionic bond depend on?
- Ionic charge
- Ionic radius
Shape and bond angle for the following molecules:
a) 2 bonding pairs
b) 3 bonding pairs
c) 2 bonding pairs + 1 lone pair
a) Linear, 180°
b) Trigonal planar, 120°
c) V-shaped, 118°
Shape and bond angle for the following 4 electron pair molecules:
a) 4 bonding pairs
b) 4 bonding pairs + 1 lone pair
c) 4 bonding pairs + 2 lone pair
a) Tetrehedral, 109°
b) Trigonal pyramidal 107°
c) V-shaped, 105°
Shape and bond angle for the following 5 electron pair molecules:
a) 5 bonding pairs
b) 4 bonding pairs + 1 lone pair
c) 3 bonding pairs + 2 lone pair
a) Trigonal bipyramid, 90° and 120°
b) no name, 119° and 89°
c) T-shape, 89°
Shape and bond angle for the following molecules:
a) 6 bonding pairs
b) 5 bonding pairs + 1 lone pair
c) 4 bonding pairs + 2 lone pair
a) Octhedral, 90°
b) Distorted square pyramid, 89°
c) Square planar, 90°
In terms of electron pairs, explain why the bond angles in a NH4+ ion are all 109°?
- 4 bonding pairs of electron
- All equally repel eachother as far apart as possible
- Creating a tetrehdral shape with 109° bond angles
What are the 3 types of IMFs?
- Hydgrogen bonds
- Permanent dipole-dipole interactions
- Van der Waals’ forces
What controls the strength of Van der Waals’?
Nuclear charge and number of electrons
What IMF is present in a molecule of SiF4? Why are no other IMFs present?
- Van der Waals’
- No H-bonds due to lack of electronegativty difference
- No permant dipole-dipole interactions as molecule is symetrical, dipoles cancel
Give the meaning of the term electronegativity?
The ability of an atom to attract a bonding pair of electrons towards itself in a covalent bond
Why does electronegativity increase from left to right across a period?
- Similar shielding
- Increased nuclear charge
- Smaller atomic radius
Why is an O-H bond in a molecule polar?
- Oxygen has high electronegativity
- Hydrogen has lower
- Oxygen atom attracts electron density
Explain how the strongest type of IMF in liquid HF arises.
- Large difference in electronegativity between hydrogen and fluorine, polar H-F bond
- Dipole: partially positive hydrogen, partially negative fluorine
- Partially positive hydrogen attracts to lone pair of electrons on fluroine
Why does boiling point of hydrogen halides increase from HCl to HI?
- Nuclear charge increases, more electrons present as you go down group
- Strong Van der Waals’
- Requires more energy to overcome
Why is the boiling point of HF the highest for all the hydrogen halides?
- Only one with hydrgoen bonds
- Stronger IMF that requires more energy to overcome
