Ionic and covalent bonding Flashcards
covalent substances are made up of…
non-metallic elements only
What are the 5 main groups all substances can be grouped into?
- metals
- ionic compounds
- simple molecular substances [covalent substances]
- giant covalent substances [covalent substances]
- macromolecules [covalent substances]
Ionic compounds are made up of?
metallic and non-metallic elements
what are macromolecules?
Very large molecules such as polymers made up by joining of many small molecules by covalent bonds
What are the giant covalent substances?
- Silicon dioxide (SiO2)
- Graphite (just carbon)
- Diamonds (just carbon)
WHAT TYpe if ions can be found in ionic compunds?
Cations and anions
What is the structure of ionic compounds?
Giant ionic lattice structure
What is the attractions present in an giant ionic lattice structure?
Strong electrostatic FOA between the oppositely charged ions that are held in fixed position within the lattice structure
What are properties of ionic compounds?
- high MP
- high BP
- conduct electricty in molten and aq state but NOT solid state
- soluble in water, insoluble in organic solvents
- hard but brittle
define ionic bond
Mutual electrostatic attraction between ions of opposite charges
How to explain why ionic compounds have high MP and BP
Structure - Ionic compounds have giant ionic lattice structure
Attraction - strong electrostatic FOA between opp charged ions
Energy - large amt of energy is needed to overcome the strong electrostatic FOA
Conclusion - Thus, ionic compounds have high BP and MP
How is it that electricity conducted in ionic compounds in molten state but not solid state?
In solid state, the strong electrostatic FOA holds the ions tgt in fixed position and since ions cannot act as mobile charge carriers, they cannot conduct electricty at Solid state.
However in molten state the electrostatic FOA is weakened due to heat energy causing them to become liquid state and thus the ions are no longer held in fixed positions.
Thus ionic compunds are mobile charge carriers in molten state but not solid state.
What is the forces in covalent bond?
- covalent bond between atoms (eg Cl2)
- intermolecular forces between molecules
why doe simple molecular substances have low MP and BP?
- they have a simple molecular structure with
- weak intermolecular forces present between molecules
- Little amt of energy needed to overcome these weak forces of attraction
- Thus the low MP and BP
Define volatile
easily evaporates at normal temp
define valency
Number of electrons that must be lost/gained/shared in order for the atom to reach a noble gas configuration
why cant simple molecular substances conduct electricity?
- They are made up of simple discrete molecules
- that are neutral and uncharged
- thus there are no mobile charge carriers to conduct electricity
Properties of simple molecular substances?
- low mp and bp
- cant conduct electricity
- insoluble in water, soluble in organic solvents
Diamonds and Graphite are _____________ of Carbon
allotropes
Giant molecular substance!
Structure:
Made up of:
Attractions present:
Structure: giant molecular structure
Made up of: atoms
Attractions present: very strong covalent bonds between atoms
define allotropes
same elements being repeated
What are the props of diamonds and SiO2?
- high MP and BP
- cannot conduct electricity
- is hard
Why does diamond and SiO2 have high Mp and BP?
Diamond has a giant molecular structure.
Each Carbon atom is covalently bonded to 4 other carbon atoms in a tetrahedral arrangement forming an extensive network of covalent bonds.
Large amt of energy needed to overcome strong covalent bonds.
Thus it has high MP and BP
why is diamond hard?
since all carbon valence electrons are engaged in a covalent bodn forming an extensive covalent network, it is difficult for carbon atoms to slide over one another.
Why cant diamond and SiO2 conduct electricty?
Each carbon atoms has used up all 4 of its valence electron to from covalent bonds with 4 other carbon atoms to form a giant covalent network. Thus, due to absence of mobile electrons, it cant conduct electricity.
What are graphites properties
- high MP and BP
- good conducters of electricity
- soft and flakes of easily
why does graphite have high mp and bp?
Graphite has a giant molecular structure.
Each Carbon atom is covalently bonded to 3 other other carbon atoms in a hexagonal plane arrangement forming an extensive network of covalent bonds.
Large amt of energy needed to overcome strong covalent bonds.
Thus it has high MP and BP
why can graphite conduct electricty
Since only 3 of the 4 valence electrons of carbon in graphite is engaged in a covalent bond, the is one valence electron that is not bonded and is delocalised between layers and acting as mobile charge carriers.
why is graphite soft and flakey?
graphite has a layered structure where the layers of carbon atoms are held together by weak intermolecular forces of attraction.
hence the layers of atom can slide over one another easily allowing carbon layers to flake of easily.
Why are ionic compounds brittle?
Ionic compounds are brittle because when enough force is applied, ions of the same charges are approach each other. The repulsive forces between ions of the same charge become larger than the attractive forces and the lattice structure shatters
Why are ionic compounds hard?
The strong forces of attraction between oppositely charged ions make ionic compounds hard and resistant to deformation, as these forces cause the ions to resist motion.
