Bonding Flashcards
as chem
what are ionic compounds and what bonds do they include?
Ionic compounds are oppositely charged ions held together by electrostatic attractions.
ionic bonds
What are the ions of
OH
NO3
NH4
SO4
CO3
OH -
NO3-
NH4+
SO42-
CO3*2-
How to do the swap and drop method for ions?
Swap the charges of 2 ions
Drop the changed charges
Simplify to the lowest whole number
What is a giant ionic structure
+
an example of a compound with this structure?
- regular structure
- cubic shape
- Giant repeating pattern
Sodium chloride has a giant ionic structure
What are properties of ionic compounds?
- most ionic compounds dissolve in water as water molecules are polar they can attract the positive and negative ions and break up the structure.
- Conduct electricity when molten or dissolved in solution as the ions are free to move around.
- High melting points as there are many strong electrostatic forces between oppositely charged ions lots of energy needed to overcome these forces.
What is covalent bonding?
Covalent bonding happens between nonmetals it is the sharing of outer electrons in order for atoms to obtain a full shell.
There is an electrostatic attraction between the shared electrons and the positive nucleus.
What is dative/coordinate bonds?
This is when one atom donates two electrons (pair of electrons) to an atom or ion to form a bond.
What are 3 examples of giant covalent structures?
Graphite and diamond and silicon dioxide
Describe properties of diamonds?
Each carbon is bonded four times in a tetrahedral shape.
The tightly packed rigid arrangement allows heat to conduct well.
Diamonds can be caught to make gemstones.
They have a very high melting point due to many strong covalent bonds. It is also very hard.
Diamonds don’t conduct the electricity well as it doesn’t have any delocalised electrons.
Diamond is insoluble as the covalent bonds are too strong to break.
Describe properties of graphite?
Each carbon bonded three times with fourth electron delocalised.
Layers slide easily as there are weak forces between the layers
Lots of strong covalent bonds means graphite has a very high melting point
Delocalised electrons between the layers allows graphite to conduct electricity as they can carry a charge
Layers are far apart in comparison to covalent bond length this means it has a low density
Graphite is insoluble the covalent bonds are too strong to break
What is the order of repulsion between type of bonds in shapes of molecules?
bond-bond pair< bond-lone pair< lone-lone pair
Meaning of electronegativity?
Electronegativity is the ability for an atom to attract electrons towards itself in a covalent bond.
What does higher electronegativity mean for polarity?
Higher electronegativity means more polar bonds
When might a polar molecule not actually be polar?
If molecules which appear to be polar are arranged symmetrically then there isn’t an overall polarity
for example CO2
Order of weakest to strongest intermolecular forces?
Strongest ———— Weakest
Hydrogen bonding
Permanent Dipole-Dipole
Van der Waals
When is a temporary/induced dipole dipole created?
This occurs when electrons in a molecule or atom moves from one end to another and only exists when two molecules or atoms are nearby.
properties of Van Der Waal forces?
Is the weakest intermolecular force.
The bigger the molecule or atom the more van Der waal forces. (higher BP)
When boiling a liquid the van Der waal forces are broken not covalent
Long straight chain hydrocarbons have more Van der Waal forces so more energy is needed to overcome these forces so the boiling point increases.
Branched hydrocarbons can’t compact close together this weakens the Van der waal forces between the chains and lowers their boiling point
Properties of dipole-diapole intermolecular forces
Permanent dipole dipole interactions exist in molecules with a polarity.
Dipole dipole is stronger than Van der Waal, but still weak.
They are the weak electrostatic forces that exist between molecules with a polarity.
Molecules who have dipole dipole interactions also have Van der Waal forces.
properties of hydrogen bonding
Hydrogen bonding is the strongest intermolecular force
Hydrogen bonding exists between NOF (nitrogen, oxygen, fluorine) and hydrogen.
Hydrogen is delta positive and the other elements are always delta negative
Properties of metallic bonding
Metals have giant lattice structures
What is a giant lattice structure?
lattice of positively charged ions surrounded by a ‘sea’ of delocalised electrons. There is an electrostatic attraction between positive metal ions and negative delocalised electrons.
Properties of metallic bonding
- The more electrons an atom can donate to the delocalised system the higher the melting point.
- Good thermal conductors as they have delocalised electrons which can transfer kinetic energy.
- Good electrical conductors as delocalised electrons can move and carry a current.
- They have high MP due to strong electrostatic attractions.
- Insoluble as metallic bond is too strong to break.
