C3 - Bonding Flashcards
An ionic bond occurs between what atoms?
A metal and a non-metal atom
A covalent bond occurs between what atoms?
2 non-metal atoms
A metallic bond occurs between what atoms?
2 metal atoms
In ionic bonds what are the 2 atoms attracted by?
Electrostatic force
Ionic compounds exist in what structure and why?
Lattices
It forms because each ion is electrostatically attracted in all directions to ions of the opposite charge.
In covalent bonds what are the 2 atoms attracted by?
Electrostatic force
What is a dative/co-ordinate bond?
A dative covalent bond is a covalent bond in which a shared pair of electrons has been supplied by one of the bonding atoms only.
How is a dative bond shown in a dot and cross diagram?
By → or ← with the arrow coming from the atom that provided the electrons
In metallic bonds what are the 2 atoms attracted by?
Electrostatic force between the metal ions and the electrons
How does metal ion size affect the strength of metallic bonds?
The smaller the metal ion, the closer the positive nucleus is to the delocalized electrons. This means there is a greater attraction between the two, which creates a stronger metallic bond.
Do ionic structures conduct electricty?
They conduct electricity when molten or dissolved in water as the ions are free to move
Do metallic structures conduct electricty?
They conduct electricity when solid or molten due to movement of delocalised electrons
Do marcomolecular structures conduct electricty?
They do not apart from graphite in a solid
Do molecular structures conduct electricty?
Does not conduct electricty as there are no charged particles
What is the boiling and melting point of ionic structures?
High as breaking strong ionic bonds requires lots of energy
What is the boiling and melting point of metallic structures?
High as breaking electrostatic forces of attraction requires lots of energy
What is the boiling and melting point of macromolecular structures?
Very high as they have many strong covalent bonds
What are the properties of ionic structures?
Hard due to strong electrostatic forces of attraction that hold ions together
What is the boiling and melting point of molecular structures?
Low as they are small structures with weak bonds
What is a molecular structure?
Simple covalent
What are the properties of metallic structures?
Malleable and Ductile as layers slide over each other
What are the properties of macromolecular structures?
Varies depending on the structure
E.g. rigid and hard for diamond but brittle for graphite
What are the properties of molecular structures?
Brittle as they don’t have strong bonds holding them together
What is macromolecular structure?
Giant covalent structure
What is a bonding pair?
A pair of electrons in a covalent bond
What is a lone pair?
Pairs of electrons that are not involved in bonding
What is bond length?
The distance between the nuclei of two bonded atoms
What is bond angle?
Angle between two covalent bonds
What is a linear shaped molecule?
2 bonding pairs around the central atom, with the 2 pairs at an angle of 180*
As well as 2 bonding pairs and 3 lone pairs
What is a traigonal planar shaped molecule?
3 bonding pairs around the central atom, with all 3 bonds on the same plane and a bond angle of 120*
What is a tetrahedral shaped molecule?
4 bonding pairs around the central atom, with a bond angle of 109.5*
What is a trigonal bipyramid shaped molecule?
5 bonding pairs around the central atom, 3 pairs in 1 plane have a bonding angle of 120, the 2 other pairs are 90 to this plane. (triagonal planar with one above and one below)
What is a octahedral shaped molecule?
6 bonding pairs around the central atom, bond angle of 90* between all the bonds.
How is the number of lone pairs calculated?
Total number of electron pairs - number of bonding pairs
What is a pyramidal shaped molecule?
3 bonding pairs, 1 lone pair, bond angle of 107*
What is a bent shaped molecule?
2 bonding pairs, 2 lone pairs, bond angle of 104.5*
What is a T-shaped molecule?
3 bonding pairs, 2 lone pairs, bond angle of 86*
What is a square planar shaped molecule?
4 bonding pairs, 2 lone pairs, bond angle of 90*
What is electronegativity?
The ability of an atom to attract a bonded pair of electrons in a covalent bond
If one atom is more electronegative than another in a covalent bond which atom are the electrons closer to?
The more electronegative atom
What direction does electronegativity increase in the periodic table?
Increases going from bottom left to top right, with fluorine being the most electronegative
Increases across a period, Decreases down a group
What 3 factors is electronegativity dependent on?
Atomic number
Atomic radius (shielding)
If an atom has its electrons closer to itself than the other atom (is more electronegative) what is its charge?
δ- (delta negative) This means it has a slight negative charge
If an atom is has its electrons further away and closer to the other atom (is less electronegative) what is its charge?
δ+ (delta positive This means it has a slight positive charge
What happens if the electronegativity of both atoms in a covalent bond is identical?
The electrons in the bond will be equally attracted to both of them. This results in a symmetrical distribution of electron density around the two atoms. So a non-polar bond is formed
What happens if the electronegativity of atoms in a covalent bond are different?
An asymmetrical distribution of electron density is created as one attracts electrons more strongly.
What is an imbalance in the charges in the bond called?
A dipole
If the electronegativity difference is 0 what is the bond type?
Covalent bond
If the electronegativity difference is between 0 and 1.8 what is the bond type?
Polar covalent with more ionic character the higher the difference
If the electronegativity difference is 1.8 or higher what is the bond type?
Ionic bond
How are the bonds arranged in a non-polar molecule?
The polar bonds are symmetrical and the partial charges will cancel out
How are the bonds arranged in a polar molecule?
The polar bonds are asymmetrical and the partial charges will not cancel out
What are the 3 types of bonding between dipoles?
Van der Vaal forces
Permanent dipole dipole forces
Hydrogen bonds
What are Van der Vaals forces
Forces of attraction due to induced dipole–dipole forces caused by movement of electrons in atoms and molecule
How can a Van der Vaal force be stronger?
By being a bigger molecule with more electrons
What are permanent dipole dipole forces?
Intermolecular force between 2 polar molecules and their δ+ and δ- charges
How can permanent dipole dipole forces be stronger?
A higher electronegativity difference which makes the charges more positive or negative
What is a hydrogen bond?
The attraction between a lone pair of electrons on one electronegative atom and an H atom bonded to either N, O of F
