Bonding Flashcards
What is ionic bonding?
strong electrostatic forces of attraction between oppositely charged ions held in a lattice
Give an example of an ionically bonded substance
NaCl (sodium chloride - salt)
Do ionic compounds conduct electricity? Why?
Yes, when molten/in solution as the ions are free to move and carry charge (don’t when solid)
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- all involved in bonding
Can simple molecular covalent molecules conduct electricity? why?
No - all electrons used in bonding and aren’t free to move.
Do simple molecular substances have a high/low melting point and boiling point? why?
Low - weak van der Waals forces of attraction between molecules that don’t take much energy to overcome (these are overcome rather than covalent bonds).
How high are ionically bonded substances’ boiling point and melting point? Why?
High - takes lots of energy to break strong electrostatic forces of attraction between oppositely charged ions
Describe macromolecular covalent bonding
Lattice of many atoms held together by strong covalent bonds
Do substances with macromolecular covalent bonds have high/low melting point and boiling points? Why?
High, as it takes a lot of energy to overcome many strong covalent bonds.
Do substances with macromolecular covalent bonds conduct electricity?
Most don’t as all electrons are used in bonding
Describe structure of diamond
3D tetrahedral structure of C atoms, with each C atom bonded to four others
Describe structure of graphite
Similar to diamond - macromolecular covalent - but each C atom is only bonded to 3 others, so it is in layers
Weak van der Waals forces of attraction 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 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 high/low boiling point and melting points? why?
High as strong forces of attraction between positive metal ions and negatively charged sea of delocalised 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 → higher Melting and boiling points, stronger Higher charge on metal ions
More delocalised electrons per ion
Stronger force of attraction between them
Define electronegativity
The ability of an atom to attract the pair of electrons (the electron density) in a covalent bond
What affects electronegativity? (3)
Nuclear charge
Atomic radius
Electron shielding
What is the most electronegative element?
Fluorine (4.0 on Pauling’s scale) → largest nuclear charge for its electron shielding, small atomic radius
How do you get a nonpolar bond?
Both bonding elements have the same electronegativities
When do you get a polar bond?
Bonding atoms have different electronegativities
What is the strongest type of inter-molecular force?
Hydrogen bonding
What is the weakest type of inter-molecular force?
van der Waals forces
