1.03 Bonding
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What is ionic bonding ?
Strong electrostatic forces of attraction between oppositely charged ions, held in a lattice structure.
Give an example of an ionically bonded substance.
NaCl.
How high are ionically bonded substances’ bp and mp ? Why ?
High - it takes lots of energy to break strong electrostatic forces of attraction between oppositely charged ions.
Do ionic compounds conduct electricity ? Why ?
Yes, when molten or in solution as the ions are free to move and carry charge.
What is simple molecular covalent bonding ?
Strong covalent bonds between atoms, weak van der Waals forces of attraction between molecules.
Are there any lone electrons in simple covalent bonding ?
No - they are all involved in bonding.
Can simple molecular covalent molecules conduct electricity ? Why ?
No - all electrons are used in bonding and aren’t free to move.
Do simple molecular substances have a high/low mpt and bpt ? Why ?
Low - weak van der Waals forces of attraction between molecules that don’t take much energy to overcome.
Describe macromolecular covalent bonding.
Lattice of many atoms held together by strong covalent bonds.
Do substances with macromolecular covalent bonds have high/low mpt / bpts ? Why ?
High, as it takes a lot of energy to overcome many strong covalent bonds.
Do substances with macromolecular bonding conduct electricity ?
Most don’t as typically all electrons are used in bonding.
Draw / describe the 3D structure of diamond.
A macromolecular covalent molecule A 3D tetrahedral structure of C atoms, with each C atom bonded to four others.
Draw / describe the structure of graphite.
A macromolecular covalent molecule Each C atom is only bonded to 3 others It comes in layers, weak van der Waals between layers mean they can slide over each other (soft / slippery) One electron from each carbon is delocalised and can carry charge (conducts electricity)
Describe and draw metallic bonding.
Lattice of positive metal ions strongly attracted to a sea of delocalised electrons Layers can slide over each other - malleable.
Do metallic compounds have a high/low mpt and bpts? Why ?
High, as strong forces of attraction between positive metal ions and negatively charged sea of electrons.
Do metallic compounds conduct electricity ? Why?
Yes as delocalised electrons can move throughout the metal to carry charge.
How does the strength of metallic bonds change across the periodic table ? Why ?
Increases as you go right, giving a higher mpt and bpt for those metals The higher charge of metal ions results in more delocalised electrons per ion This gives a stronger force of attraction in turn.
Define electronegativity.
The ability of an atom to attract a pair of electron in a covalent bond.
What affects electronegativity ?
Nuclear charge Atomic radius/electron shielding
What is the most electronegative element ?
Fluorine (4.0) This is because it has the largest nuclear charge for its electron shielding and a small atomic radius.
How do you get a nonpolar bond ?
Both bonding elements have similar electronegativities.
When do you get a polar bond ?
Bonding atoms have different enough electronegativities.
What is the strongest type of intermolecular force ?
Hydrogen bonding.
What is the weakest type of intermolecular force ?
Van der waals forces.