Bonding and Structure Flashcards
Ion
A charged particle formed when an atom loses or gains electrons
Molecular ion
A charged particle containing more than one atom
Cation
A positive ion
Anion
A negative ion
Electrostatic attraction
An attractive force which 2 unlike charges exert on each other when they are kept some finite distance apart
Molecule
A particle that consists of two or more atoms chemically bonded together
Diatomic molecule
Two atoms covalently bonded in a molecule
Allotrope
Different forms of the same element in the same state
Covalent bond
Formed by a shared pair of electrons
Ionic bond
The attraction between oppositely charged ions
Van der waal’s forces
Weak intermolecular forces which exist between covalently bonded molecules
Metallic bond
The attraction between delocalised electrons and the positive ions in a regular lattice
Delocalised electrons
Electrons that are free to move throughout the whole structure
Malleable
Can be hammered into shape
Ductile
Can be drawn out into wires
Alloy
A mixture of two or more elements at least one of which is a metal and the resulting mixture has metallic properties
Bonding
Describes how atoms or ions are held together
Structure
Describes how atoms or ions are arranged in space
Describe Ionic bonding
-Happens between metals and non-metals
-In Ionic bonding atoms will lose or gain electrons to have full outer shells
-Ions are produced
-The oppositely charged ions attract each other
Describe Covalent bonding
-Involves sharing of electron pairs usually one electron from each atom
-Takes place in non metal elements and compounds of non metal elements
-Produces uncharged molecules
-Shared electrons are counted as outer shell electrons for both atoms
What is a lone pair
Pairs of electrons in the outer shell which are not used up in bonding
Metallic bonding
-Occurs between metal elements and alloys
-Metallic bonding is the attraction between delocalised electrons and the positive ions in a regular lattice
The outer electrons are delocalized
What is the ionic bonding structure
Giant Ionic Lattice
What is an ionic lattice
A 3D structure of oppositely charged ions held together by electrostatic forces of attraction called ionic bonds
Name three properties of ionic compounds
-High melting and boiling points
-Conduct electricity when molten or in a solution but not when solid
-Soluble in water
Why do ionic compounds have a high melting, boiling point
A lot of energy is required to break the strong ionic bonds (electrostatic attraction) between the ions in the giant structure
Why do ionic compounds conduct when molten or in a solution but not when solid
An electric flow of charged particles(either electrons or ions). Ions are free to move and carry charge when compound is a liquid or solution but not when it is solid
Name the properties of molecular covalent compounds
-Low melting and boiling points
-Doesn’t conduct electricity
-Low solubility in water but dissolves in solvents
Why molecular covalent compounds have a low melting boiling point
Little energy is required to break the weak van der waal’s forces between the molecules. The strong covalent bonds in the molecule don’t break
Why do molecular covalent compounds not conduct electricity
The molecules are neutral and therefore they have no free electrons or ions to move and carry charge
What is an allotrope
Are different forms of the same element in the same state
What are the allotropes of carbon
diamond graphite graphene
The structure of Diamond
Millions of covalent bonds. Each carbon atom is covalently bonded to 4 others in a tetrahedral arrangement in a giant covalent structure
The structure of graphite
Each carbon atom is covalently bonded to three others in hexagonal rings producing layers of carbon atoms with weak van der waal forces of attraction between the layers it has a giant structure containing millions of carbon atoms
The structure of graphene
A single atom thick layer of graphite with strong covalent bonds between each carbon atom the atoms are arranged in hexagons it is considered a 2D giant covalent structure
What are the properties of diamond
-Very high melting point
-Insoluble water
-Does not conduct
-Hard
-Used in cutting tools and drill bits
What are the properties of graphite
-Very high melting point
-Insoluble in water
-Good conductor
-Soft
-Used for lubricants for machinery and in pencil leads
What are the properties of graphene
-Very high melting point
-All insoluble in water
-Good conductor
-Very strong
-Used in solar cells and batteries of the future
Why do diamond, graphite and graphene have a high melting point
A lot of energy is required to break the strong covalent bonds between the atoms in the giant structure
Why does diamond not conduct
All outer electrons are bonded there are no free ions or electrons to move and carry charge
Why are graphite and graphene good conductors
One outer electron per atom is unbonded this electron is delocalised and free to move and carry charge
Why is graphene a better conductor than graphite
The 2D structure offers little resistance to the flow of electrons
Why is diamond hard
Due to the 3D tetrahedral structure with strong covalent bonds throughout
Why is graphite soft
The layers of carbon atoms can slide over each other as the weak van der waal forces between the layers are easy to break
Why is graphene strong
Due to the strong covalent bonds within the layer structure
Metallic Structure
-High density as the ions are tightly packed in a small space
-Quite hard as the metallic bond requires a lot of energy to break
Name the properties of metals and alloys
-Usually high melting and boiling point
-Conduct electricity
-Malleable and ductile
Why do metals and alloys have a high melting and boiling point
A lot of energy is required to break the strong metallic bonds between the positive ions and delocalised electrons in the giant structure
Why do metals and alloys conduct electricity
Contain delocalised electros which move and carry charge
Why are metals and alloys malleable and ductile
The layers of ions can slide over each other without the metallic bonds breaking as the delocalised electrons still attract the ions
How to calculate the % of gold in alloy
(number of carats X100) divided by 24
What is the use and purpose of Stainless steel
Sinks and cutlery and it is alloyed as it is more resistant to rusting
What is the use and purpose of solder
Soldering joints and it is alloyed as it lowers the melting point
What is the use and purpose of brass
For decorative work and it is alloyed as it has a nice colour and is hard
What is use and purpose of 18 carat gold
Jewellery and is alloyed for harder wearing
