CHEM 3.1.3 - Bonding (includes polarity) UNFINISHED

tuff ahh diddenbludden

define ionic bonding

electrostatic force of attraction between oppositely charged ions

describe why the structure and bonding in NaCl gives it a high m.p and b.p

ions arranged in an ionic lattice where each cation surrounded by and strongly attracted to several anions and vice versa

factors that affect strength of ionic bonding

more charge = stronger

smaller ion = stronger

trend in ionic radius across a period

varies:

• as cations lose e- they get smaller by losing a shell

• as anions gain e- they get bigger by gaining a shell

• but either way as nuclear charge increases ionic radius decreases

Properties of ionic compounds

High b.p (strong forces of attraction)

conducts electricity when molten or aqueous

hard

define metallic bonding

strong electrostatic force of attraction between metal ions and delocalised electrons

properties of metallic compounds

high m.p and b.p

conducts electricity (delocalised e- can move)

strong but also malleable and ductile since layers can slide over eachother without disrupting the metallic bonds

define covalent bonding

electrostatic force of attraction between 2 nuclei and their shared pair of e-

Properties of simple molecular compounds

low b.p (weaker IM forces)

does not conduct electricity

soft

Properties of macromolecular compounds

High b.p (network of strong covalent bonds)

doesn’t conduct electricity (except graphite w/ its delocalised e-)

hard (graphite is soft because carbon layers and sea of delocalised electrons)

what are electron deficient species

species that do not form a full outer shell when forming compounds

example of electron deficient compound

BF₃

how do electron deficient compounds form

• because some group 3 metals have very high ionisation energies

• it is preferable to form covalent bonds even if a full outer shell is not completed

how do expanded octets happen

• for elements in group 3 or above (has a d-subshell)

• e- can be ‘promoted’ to the d-subshell OF THE SAME SHELL allowing more bonds to be made

• so more than 4 pairs of e- can surround the nucleus

3 examples of expanded octet compound

PCl_5, PF₅, SF₆

how do co-ordinate/dative bonds form

one atom (can be in a molecule) donates both of the e- for a covalent bond; doesn’t affect properties.

what is the notation for a co-ordinate bond (in displayed formula/lewis structures)

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