chemical bonding

What is an ion?

Charged particle formed when an atom or group of atoms loses or gains electrons to achieve noble gas configuration

How do atoms form ions

Atoms lose or gains electrons electrons to achieve noble gas configuration

Metal atoms lose electrons to form cation

Non metal atoms gain electrons to form anions

Compare atoms and ions

Similarity: same number of protons and neutrons

Difference: different number of electrons (best to specify)

How ionic bonds are formed

Metal atoms lose valence electrons to form cation

Non metal atoms gain electrons to form anion

Cation and anion are held together by strong ionic bonds (must quote atom and charge of ion)

What is giant ionic lattice

Repetition of uncountable number/ large number of ions arranged in orderly manner throughout whole structure

Physical properties of ionic structure

1. High melting and boiling points

2. Conduct electricity in molten and aqueous states but not solid

3. Hard

4. Dissolve in water, cannot dissolve in organic solvents (no reason why)

1. Why ionic structures have high melting and boiling points

• Have giant lattice structures

• Ionic bonds are very strong

  Hence large amount of energy needed to overcome very strong ionic bonds

2. Electrical conductivity of ionic compounds

• can’t conduct in solids: ions in fixed positions, no mobile ions

• Conduct in molten and aqueous states: presence of free mobile ions

3. Why ionic structures are hard

Ions held by many very strong ionic bonds throughout the whole structure

Compare covalent and ionic structures

Similarity

• purpose of both types of bonding is to achieve noble gas configuration

• Both bonding very strong

  Difference:

• covalent is sharing of electrons while ionic is transfer of electrons

• Covalent involves non metals atoms only while ionic involves metal and non metal atoms

• Covalent present in both elements and compounds while ionic bonding present only in compounds

What is a molecule

Made of of two or more atoms covalently bonded together

What is diatomic molecule

2 atoms covalently bonded together (atoms can be from the same or different element)

Physical properties of simple covalent structures

1. Low melting points

2. Do not conduct electricity

3. Can’t dissolve in water but dissolve in organic solvents (Except hydrogen chloride, ammonia, carbon dioxide) no reason

1. Why simple covalently structure low melting points

• simple covalently structures

  Hence little energy needed to overcome weak intermolecular forces of attraction between molecules

2. Why simple covalently structure molecules can’t conduct electricity

• no mobile electrons (since all electrons are found within atoms or involved in covalent bonding)

Bonding of diamond

• Uncountable number of strong covalently bonds between atoms (single bond)

• Every carbon is covalently nodded to 4 other carbon atoms

Structure of diamond

• giant covalent structure

• Tetrahedral shape

Formula of diamond

C (lowest ratio)

Physical properties of diamond

1. High melting point

2. Very hard

3. Can’t conduct electricity

4. Cannot dissolve in any solvents

1. Why diamond has high melting point

• Giant covalent structure

  Hence a lot of energy needed to break numerous strong covalent bonds between atoms

2. Why diamond very hard

• Numerous strong covalent bods between atoms in all directions

3. Why can’t conduct electricity

• no mobile ions

• No mobile electrons (all electrons are found within atom or involved in covalent bonding)

4. Why diamond insouble in all solvents

• had giant covalent structure

Bonding of silicon dioxide

• numerous covalent bonds between atoms

• Each silicon atom is covalently bonded to 2 oxygen atoms

• Each oxygen atom is covalently bonded to 2 silicon atoms

Formula of sand/ silicon dioxide/ silica

SiO2

Structure of sand

• Giant covalent structure

Physical properties of silicon dioxide

Same as diamond

Bonding of graphite

• numerous strong covalent bonds between atoms

• Every carbon atom covalently bonded together 3 other carbon atoms

• Weak forces of attraction between layers of carbon atoms

Structure of graphite

• giant covalent structure

• Layered structure

• Hexagonal rings

Formula for graphite

C

Physical properties of graphite

1. High melting point

2. Soft and slippery

3. Can conduct electricity

4. Can’t dissolve in any solvents

1. Why graphite has high melting point

• giant covalent structure

  Hence a lot of energy needed to break the numerous strong covalent bonds between atoms

  (Diamond has higher melting point than graphite as diamond has more covalent bonds)

2. Why is graphite soft and slippery

• layers of carbon held together. By weak intermolecular forces of attraction

  Hence when little force is applied, weak forces of attraction easily broken, causing layers of carbon atoms to slide past one another

3. Why graphite can conduct electricity

• each carbon bonded together 3 other carbon atoms, 4th non bonding electron is delocalised and mobile

  Hence has mobile electrons throughout layer that allows graphite to conduct electricity

4. Why graphite insoluble in any solvents

• Has giant covalent structure

What are allotropes

Different forms of the same element with different physical properties

Same chemical properties as from same element