EL5- Molecules Of Life Flashcards
Covalent bonds form between…
Non-metals
In covalent bonds, pairs of electrons are…
Shared
What are dative covalent bonds?
- when 1 atom provides both electrons for bond
What are the physical properties of covalently bonded simple molecules?
- intramolecular forces WITHIN molecule are strong
- electrostatic attractions between different molecules are weak, therefore small amounts of energy needed to separate bonds (low mp and bp)
Why don’t covalently bonded molecules conduct electricity?
There are no charged particles (no sea of delocalised electrons)
What is the shape of a structure with 4 bonding pairs of electrons, and what is the bond angle between electrons?
- tetrahedral
- 109.5
How many bonding and lone pairs of electrons are there in a pyramidal shaped molecule? And what are the bond angles?
- 3 covalent bonds, 1 lone pair
- 107
What is the shape of a structure with 2 covalent bonds and 2 lone pairs of electrons? And what are the bond angles?
- non-linear
- 104.5
How many bonding pairs of electrons has a molecule with a trigonometry pyramid shape? And what are the bond angles?
- 5 bonds
- 90 or 120 depending on position
What are the bond angles in a molecule with an octahedral shape?
90
By how much do lone pairs of electrons reduce the angle size by in covalently bonded molecules?
2.5
What happens when iodine (simple structure) is melted?
- weak intermolecular forces in crystal lattice are broken
- strong intramolecular covalent forces are not broken
Why does diamond have a high melting point?
- every carbon atom is covalently bonded to 4 other carbons, takes a lot of energy to break strong covalent bonds
Why does graphite conduct electricity?
- each carbon is covalently bonded to 3 others, therefore there is 1 delocalised electron per carbon atom
- delocalised electrons are negatively charged and conduct electricity
