Bonding, Structure and Properties 1.3 Flashcards
(17 cards)
Why do Noble gases not form compounds
The noble gases do not bond with other atoms because they have a full outer energy level.
- Non-metal atoms bond together by sharing electrons to achieve a full outer energy level.
- The number of bonds which an atom can form is equal to the number of electrons that are needed to fill the outer energy level.
What is a covalent bond
- A shared pair of electrons between 2 non-metal atoms
- Only the outer electrons are involved in bonding
What is the strong bond between atoms
The strong bond that is formed between atoms that are joined by covalent bonds is the result of electrostatic attraction between the positive nuclei of the atoms and the pairs of negative electrons that are shaped between them.
Covalent Molecules
Covalent molecules have atoms connected by covalent bonds. The molecules are separate from the other molecules and only have very weak forces of attraction holding them near each other
Covalent Networks
Covalent networks have all the atoms connected to their neighbours with covalent bonds.The element carbon and the compound silicon dioxide are examples of covalent networks.
Conduction
Electricity is a flow of charged particles.
A flow of electricity is called an electric current.
Materials that conduct electricity are called conductors.
Materials that do not conduct electricity are called insulators.
Conduction in covalent compounds
Covalent compounds do not conduct electricity.
Covalent compounds have no charged particles to carry a current.
They are insulators.
- (Graphite is an exception)
Melting and Boiling Points of COVALENT COMPOUNDS
-Covalent bonds are strong bonds.
In a covalent network every atom is connected to its neighbours by a strong covalent bond. Since covalent bonds are strong, it takes a lot of energy to break up the network,
- Covalent molecules have strong covalent bonds joining the atoms inside the molecule, but between one molecule and another there are only weak forces of attraction.
- The weak forces of attraction can be easily overcome—the reason why water is a liquid at room temperature.
- Covalent molecular substances have low melting and boiling points, i.e. they are usually liquids or gases at room temperature
Ionic Bonding
When a metal is reacted with a non-metal, the metal atoms lose electrons to the non-metal, giving the non-metal a negative charge.The resulting positive metal ions are strongly attracted to the negative non-metal ions.
Ionic Formulas
They must show charges on each ion
Ions in crystal lattice
ions in a crystal lattice are held together by strong electrostatic forces of attraction between the positive and negative ions
Ionic Compounds and their conductivity
When they are in a solid state the ions are attracted and can’t move so electricty can’t pass around. In a liquid state the ions can move around and pass electricity.
What happens when electrolysis happens
The negative ions(non-metal) are attracted to the positive electrode and the positive ions(metals) are attracted to the negative electrode:
What is Electrolysis?
The passage of electricity through a solution or melt (molten ionic compound) to break up an ionic compound is called electrolysis.
Reason they are hard to break
IONIC LATTICE-All ionic compounds have a high melting point and boiling point because many strong ionic bonds need to be broken.
COVALENT NETWORK -All covalent network structures have very high melting points and boiling points because many strong covalent bonds need to be broken.
COVALENT MOLECULAR-They have low melting points and boiling points because the attractions between molecules are easy to overcome. The strong covalent bonds are not broken .
What is a solvent
A liquid in which substances can dissolve
Solubility
Most covalent compounds dissolve in non-aqueous solvents but not water
