Bonding Flashcards
What are the properties of covalent bonds
Low melting and boiling point due to weak intermolecular forces These intermolecular forces are increased with molecular size e.g. there are bigger forces between C2H6 than CH4
Why do covalent bonds have a shared pair of electrons
To gain a noble gas configuration
What is an ionic bond
The type of bonding that occurs between a metal and a non-metal An electrostatic attraction between type oppositely charged ions
What does the electrostatic attraction cause
The formation of +ve and -ve ions with stable noble gas configurations
Properties of ionic bonding
Ionic lattices - ionic solids are often crystalline The ions are arranged in a giant 3D lattice pf alternating +ve and -ve ions Strong electrostatic attraction between the anions and cations, this causes high melting and boiling points
What is metallic bonding
The bonding found between two metals
What is a metallic bond
Electrostatic attraction between metals ions and a sea of delocalised electrons
Why are metallic bonds good conductors
The electrons are free to move
Why do metallically bonded compounds have high melting and boiling points
Because the electrostatic attraction between positive metal ions and delocalised electrons is strong
How does electrostatic attraction change is the metal becomes more malleable
The electrostatic attraction weakens
What is the difference between ionic and covalent bonds?
Ionic bonds are crystalline solids whereas covalent bonds are liquids or gases Ionic has high b.p./m.p. and covalent has low b.p./m.p. Ionic bonds are soluble in water and covalent bonds aren’t Ionic bonds aren’t soluble in organic solvent but covalent bonds are Ionic bonds conduct electricity in molten or solution state whereas covalent bonds do not
Why can ionic bonds conduct electricity in molten or solution state
Because the ions are free to move and carry charge
Why can’t covalent bonds conduct electricity
There are no charged particles to carry charge
Define allotropy
The substance has more than one form that can occur in a physical state
Examples of carbon allotropes
Diamond, graphite, graphene, buckminsterfullerene (C60)
Describe the properties of graphite
Electrically conductive Black, opaque, shiny density 2.25g/cm3
Describe the properties of diamond
Electrical insulator Transparent, shiny, sparkles Hardest known substance 3.52g/cm3
Describe bonding of graphite
Layered structure Hexagonal patterns within layers Strong bonds within layer Weak forces between layers Spare electron per carbon atoms leads to electrical conductivity between layers
Why is graphite a good lubricant
The weak forces between layers
Describe properties and structure of diamond
Tetrahedral arrangement Each C atom bonds with four others Strong bonds with no spare electron making it a good insulator Shape of diamond makes it very hard
What structures do graphite and diamond have
Giant structures
Describe the properties of silicon (IV) oxide
High mpt and bpt Isn’t electrically conductive Hard but not as hard as diamond which is 8 times harder
How many types of bonding are there?
3 - metallic, ionic, covalent
Why do giant ionic lattices have a high melting and boiling point
Strong electrostatic forces of attraction between oppositely-charged ions require a lot of energy to break
When don’t and do ionic compounds conduct electricity
They don’t in solid state They do in liquid and molten state
Why do ionic compounds conduct electricity in molten or liquid state
Because the IONS are free to move
As you go down the group 1 what happens to reactivity and why?
Reactivity increases with a larger electron configuration The outer electrons are further away from the nucleus The attraction between the nucleus and valence electron gets weaker This allows it to react more readily
Why do noble gases not readily react
They have complete outer shells There is no need to lose or gain electrons Therefore they are inert
How is a covalent bond formed
the two non-metals share a pair of electrons
Why are simple molecular structures solid, liquid or gas and a low melting or boiling point
They have strong covalent bonds but weak intermolecular forces When a covalent substance melts or boils its the weaker intermolecular forces that break Less energy is required to break these molecules apart, so they have a lower m.p or b.p
Why does a substance with a large molecular mass have a high boiling point
It means there are more covalent bonds in the structure Therefore more energy required to break more bonds
Why do giant covalent structures have high m.p and b.p
Because it has a large amount of strong covalent bonds which take large amounts of thermal energy to break
Do covalent compounds conduct electricity
Not usually
Draw a 2d metal lattice
What is metallic bonding (refer to electrostatic attraction)
The electrostatic attraction between positively charged metal ions and a sea of delocalised electrons
Why are metals electrical conductors
There are free electrons able to move and carry charge
Electrons entering the other end of the metal cause a delocalised electron to displace
Hence electrons can flow so electricity is conducted
Why are metals malleable
There are layers of +ve ions that can slide over one another when a force is applied.
The metallic bonding allows the metal to change shape without shattering
What is a metal alloy
A mixture of a metal and one or more other elements
Usually another metal and carbon
Why are metal alloys harder than pure metals
The alloy is made up of atoms of different size
This means that the layers of atoms cannot slide over each other easily
This makes the metal harder
Uses of aluminium
Aircraft - low density/ resists corrosion
Power cables - conducts electricity/ ductile
Uses of copper
water Pipes - maleable/ below hydrogen in reactivity series so it doesn’t react with water
Electrical wiring - excellent conductor of electricity
Uses of iron
Power cables - good electrical conductor
Window frames - reistant to corrosion
Aeroplanes - high strength to weight ratio
Uses of low carbon
Car bodies - malleable
Uses of high-carbon steel
Used for construction - strength
Uses of stainless steel
Cutlery - doesnt rust
