Bonding Flashcards
What is ionic bonding?
Strong electrostatic forces of attraction between oppositely charged ions.
Why do ionic compounds have high mp/bps?
They have strong electrostatic forces which take lots of energy to break.
When do ionic compounds conduct electricity?
When molten or dissolved in a solvent, as the ions are mobile and can carry charge.
What is simple molecular bonding?
Strong covalent bonds between atoms, but they have weak van der waals forces of attraction between molecules.
Do lone pairs exist in simple covalent bonding?
No, all electrons are involved in bonding.
When can simple molecular molecules conduct electricity?
Never - all of the electrons are used in bonding, so can’t move / carry charge
Why do simple molecules substances have a low mp/bp?
They have weak Van der Waal intermolecular forces which do not require a lot of energy to break
What is macromolecular covalent bonding?
Lattice of many atoms held together by strong covalent bonds.
Why do substances with macromolecular covalent bonds have high/low molecular/bps?
It takes a lot of energy to overcome many strong covalent bonds.
Describe the structure of diamond.
3D tetrahedral structure of C atoms, where each C is bonded to 4 other carbon atoms
Describe the structure of graphite.
- each carbon is bonded to 3 other Cs
- weak VDWs between layers so layers can slide over each other
- one electron from each carbon is delocalised so can carry charge and conduc electricity
What is metallic bonding?
Bond between metals, creating a lattice of metal ions kept together with a sea of delocalised electrons. (So can carry charge)
Layers can slide over each other, malleable.
Why do metallic compounds have a high mp/bp?
They have strong forces of attraction between the metal ions and the delocalised electrons
What affects the strength of metallic bonds?
Charge of metal ions - the higher the charge, the stronger the bond as there are more delocalised electrons s and the force of attraction will get stronger
What is electronegativity?
The ability of an atom to attract the pair of electrons within a covalent bond
What 3 things affect electronegativity?
- nuclear charge
- atomic radius
- shielding
What is a polar molecule?
A covalent molecule where one element is more electronegative than the other, so there are partial charges on the elements in the compound.
What is a non-polar compound?
A covalent compound where both bonding elements have similar or the same electronegativity.
What are the types of intermolecular forces?
Hydrogen bonding, Induced dipole-dipole, and permanent dipole-dipole
What is the order of strength of intermolecular forces? (Low to high)
Induced dipole-dipole → permanent dipole-dipole → hydrogen bonding.
What is Van der Waals forces?
Temporary dipoles are created by the random movement of electrons, which induces a dipole in a neighbouring molecule due to the repulsion of negative charges. This becomes a temporary, induced dipole.
When are VDWs stronger?
Larger molecules, as there are more electrons
What is a permanent dipole-dipole?
Polar molecules have permanent dipoles, forces of attraction between dipoles and that of neighbouring molecules
When does H bonding occur?
in O-H, N-H or F-H bonds, with a lone pair on the O, N or F.
Why does H bonding occur?
O, N and F are highly electronegative, leaving the H nucleus exposed. There is a strong force of attraction between the H and the lone pair on O, N, F.
Why is ice less dense than liquid water?
Liquid water has H bonds which are constantly breaking and reforming as the molecules move around.
In ice, the H bonds are slightly further apart than in liquid water as they are held in fixed positions.
What is a dative (co-ordinate) covalent bond?
Formed when an electron deficient atom accepts a lone pair of electrons from another atom or ion.
How is a dative covalent bond represented?
→
What does the Electron Pair Repulsion Theory state?
Electron pairs will take positions as far away from each other as possible, to minimise repulsion between them.
What type of electron pair is the most repulsive?
Lone pairs have the strongest repulsion.
