Chemical Bonds
METALLIC BOND
Metal to metal bond
Metals LOSE Electrons to gain full outer shells
IONIC BOND
Metal to Non-metal bond
COVELENT BOND
Non-metal to Non-metal
Non-Metals GAIN Electrons to gain full outer shells
NOTE: Group 0 elements - already have full outer shell
Very stable already
Do not form bonds
Unreactive
Metals - release outermost electrons
Metal atoms - become positive ions (as they now have more protons than electrons)
SEA OF DELOCALISED ELECTRONS
Form METALS
Orderly arrangement of positive ions surrounded by a sea of delocalized electrons
Electrons in sea - can move freely carrying ELECTRICTY + HEAT ENERGY
Conducts heat
Layers of ions - can slide over each other when hammered or stretched
(Electrons 'moved/displaced' by this can still bond)
Malleable
Ductile
STRONG ATTRACTION between POSITIVE IONS and the DELOCALISED ELECTRONS
DEFENITION: strong electrostatic attraction between the closely packed positive metal ions and the sea of delocalised electrons
Strong
High melting point + Boiling Point
MELTING POINT increases as GROUP increases
Group 2
Group 1
1 Outer electron
2 Outer electrons
each atom releases 2 electrons into sea of delocalised electrons
Metal ions: 2+ charge
each atom releases 1 electron into sea of delocalised electrons
Attraction between:
Same number of metal ions (each with 2* the charge compared to group 1 (2+ charge))
2* number of electrons compared to group 1(each with 1- charge)
Metallic Bond - stronger for Group 2 than for Group 1
Metal ions: 1+ charge
electrons TRANSFERED from METAL atom -> NON METAL atom
Metal atom - Lose electrons
Non-Metal atom - Gain electrons
Form negative ions
Form positive ions
Ions - OPPOSITE CHARGES
ATTRACT each other
DEFENITION: Strong electrostatic attraction between oppositely charged ions
Shown using DOT CROSS DIAGRAMS
when drawing diagrams, only draw OUTERMOST shell
MUST DRAW FOR FULL MARKS:
Atoms BEFORE
Electrons transfer
Ions formed
doesn't cause ions to repell
like what happens in IONIC BONDS
High melting + Boiling point
Conducts electricty
Form (GIANT) IONIC STRUCTURES
Ionic lattice
the regular arrangement of the ions in ionic structures
The oppositely charged ions attract each
other in a regular pattern
SOLID
DISSOLVED/MOLTEN
Ions - free to move/carry charge
Ions - fixed in position + cannot move
Conducts Electricity
Doesn't Conduct Electricity
Free Ions - can bond with water molecules
Soluble in water
External force applied
Layers slide past one another
same charges repel each other
Brittle
Orderly array of oppositely charged ions
Forms GIANT COVALENT STRUCTURES
a.k.a giant molecular structures
Forms SIMPLE COVALENT STRUCTURES
'shells' are also known as 'orbitals'
Non-Metals atoms share electrons to gain full outer shells
(As no supply of extra electrons is available)
(As no METALS)
(SINGLE) covalent bond
DOUBLE covalent bond
TRIPLE covalent bond
2 PAIRS of shared electrons
3 PAIRS of shared electrons
1 PAIR of shared electrons
Drawn as: X-X
Drawn as: X=X
Definition: A very strong bond between 2 non-metal atoms, where atoms share pair/s of electrons to gain full outermost shells
small covalent molecules
STRONG covalent bonds BETWEEN ATOMS
WEAK force of attraction (weak intermolecular
forces) BETWEEN MOLECULES
Easy to break
Low melting + boiling point
Usually liquids/gas at room temp.
LOW density
a.k.a simple molecular structures
NO CHARGES
No free electrons/ions
DOES NOT conduct electricity
Contain REPEATING structures of STRONG COVELENT BONDS
Diamond
Graphite
Each Carbon forms 4 STRONG covalent bonds to other atoms
All Electrons Used to bond
COULD have free electrons/ions (depending on structure)
Each Carbon forms 3 STRONG covalent bonds to other atoms
Forms HEXAGONAL LAYERS
1 other electron in each atom (not used for covalent bonding)
lost to a SEA OF DELOCALISED ELECTRONS
(As only 3 covenant bonds)
Contrast - 4 in diamond - where all electrons are used in covalent bonding
Strong bonds in all directions
No free electrons
Does NOT conduct heat/electricity
Very Hard
Very high melting (+ boiling) point
Used for: cutting tools + drill bits
WEAK FORCES BETWEEN LAYERS
Layers can slide over each other
Soft
Strong bonds in layers
High melting (+ Boiling) point
SEA OF DELOCALISED ELECTRONS present
very good electrical conductor
Used for: Electrodes
Used for: Lubricant + Pencils
Fullerenes
Large CLASS of allotropes of Carbon
Carbon nano-tubes
Graphene
Allotropes - different forms of the same element
e.g. diamond, graphite, fullerenes, carbon nanotubes are allotropes of Carbon
Made of balls/cages/tubes of carbon atoms
Single layer of a Graphite molecule
Bonded together in HEXAGONAL HONEYCOMB LATTICE
Thinnest material (currently known)
Best (currently known) conductor of heat + electricity
Unreactive
Very strong 100x-300x stronger than steel)
Carbon nano-tubes - type of Fullerene
Layers of graphite rolled into a tube
1 free electron per carbon because of the rolled up structure
Very good electrical conductor
Extremely strong
Individual atoms of Carbon DONT HAVE THE SAME PROPERTIES as bulk materials (e.g. the bulk material diamond, carbon nano-tubes)
Shown using DOT CROSS DIAGRAMS
when drawing diagrams, only draw OUTERMOST shell
'X' for one atoms electrons, '.' for the other's
'X' for one atoms electrons, '.' for the other's
Seethrough
Light
Chemical bonding
When atoms bond together
to achieve a full outermost shell/orbital of electrons
By sharing delocalised electrons - strong metallic
bonds are formed between metal atoms
Metal - Higher group
Metal - must lose more electrons to gain full outer shell
Each atom has a greater positive charge - greater number of electrons, so greater difference between number of protons and electrons
More electrons in sea of electrons - release more electrons into sea of electrons per atom
Attraction - between greater number of electrons, and Metal ions with a greater charge
Metallic bond - much stronger here
More difficult/greater energy required to break bonds
Melting point + Boiling point greater
To achieve a FULL outermost orbital of electrons (for both the metals and non-metals)