Bonding Flashcards
(47 cards)
What are the 3 types of bonds?
Ionic bonds
Covalent bonds
Metallic bonds
When does ionic bonding occur?
Between a metal and non-metal
When are positive and negative ions created?
Positive ions are created when an atom LOSES electrons
Negative ions are created when an atom GAINS electrons
How is ionic bonding shown in a diagram?
Dot and cross diagram
Transfer of electrons (dot/cross) between outer shells of two atoms shown through arrows
Must show two stages of process: one showing transfer and other showing result
What are ionic compounds held together by?
The attraction between oppositely charged ions/electrostatic forces/ionic bonds (all the same)
What do all ionic compounds exist as?
Giant ionic structures - Many ions joined to each other with ionic bonds in a giant ionic lattice
What are the properties of ionic compounds?
Generally soluble - Water molecules are attracted to charged ions
High mpt and bpt - Strong bonds between oppositely charged ions are hard to break
Do not conduct electricity when solid - Ions firmly held together in lattice (+ no free electrons)
Do conduct electricity when molten - Ions are free to move
Why is the melting temperature higher on a compound containing ions with higher charges?
The higher the charges on ions are in an ionic compound, the stronger the forces of attraction are, therefore making them harder to break
When does covalent bonding occur?
Between two non-metals
What happens in ionic bonding?
Electrons are transferred between atoms to create a full outer shell and become ions
What happens in covalent bonding?
Two ions (either different or the same) share electrons to achieve a full outer shell
How is covalent bonding shown?
In one diagram in which the shared electrons are depicted between the two ions
Why are covalent bonds strong?
The shared electrons are attracted to the nuclei of both atoms
What do most covalently bonded structures exist as?
Simple molecular structures
What forces of attraction are present in substances with a simple molecular structure?
Strong covalent bonds between atoms (intramolecular forces), but weak intermolecular forces (forces of attraction between individual molecules - hence low mpt and bpt)
What properties do simple molecular structures have?
Low mpt and bpt - Liquids and gases at room temp
Do not conduct electricity - No delocalised electrons
Which covalent substances exist as giant structures?
Diamond + Graphite
What properties does graphite have?
Very soft
Conducts electricity - sea of free moving electrons because fourth electron is unbonded
Very high mpt - Over 3600 degrees
Describe the structure of graphite
Made of C atoms
Layers of hexagonal structures
Each C atom joined to 3 others
Fourth electron is delocalised between layers
Strong covalent bonds between C atoms but weak forces of attraction between layers
What are the uses of graphite?
Pencils + lubricants - Layers can slide because of weak forces of attraction
Electrodes
Describe the structure of diamond?
A form of C
Each C atom is joined to 4 others
What are the properties and uses of diamond?
V. hard -> Cutting tools
V. high mpt + bpt
Crystalline -> Jewellery
Does not conduct electricity
What are metallic bonds?
Forces of attraction between positive metal ions and delocalised electrons
Describe metallic structures
Giant structures of regularly arranged metal atoms in a lattice in a ‘sea’ of delocalised electrons which are free to move around the lattice