bonding and structures

what is ionic bonding between?

metal + non-metal

how does ionic bonding take place?

metal transfers electrons to non-metal

forms ions

how is a giant ionic lattice formed?

oppositely charged ions attract via electrostatic forces

what is covalent bonding between?

2 non-metals that share pairs of electrons

what is dative bonding?

type of covalent bonding

→ shared electrons only come from a single atom

→ indicated by arrow from the lone pair

what is metallic bonding?

lattice of +ions surrounded by delocalised electrons

→ produced a strong electrostatic force of attraction

why do larger ions produce a weaker attraction?

greater atomic radius

what are physical properties of elements?

BP, MP, solubility and conductivity

properties of ionic crystal structures?

high MP + BP

conduct electricity when molten/in solution

brittle

why do ionic crystal structures have high BP + MP?

electrostatic forces holding ionic lattice together are strong

why can ionic crystal structures conduct electricity when molten/in solution?

no lattice; ions free to move and carry charge

why are ionic crystal structures brittle?

when force applied, layers of alternating charge are distorted

like charges repel, breaking lattice into fragments

example of an ionic crystal structure?

sodium chloride

properties of metallic crystal structures?

good conductors

→ delocalised electrons move + carry charge

malleable

high MP + solid at room temp apart from mercury

→ +ions and D electrons have strong electrostatic forces of attraction

why are metallic crystal structures malleable?

layers of +ions can slide over each other

→ the delocalised electrons prevent fragmentation as they can move around the lattice

properties of simple molecular crystal structures?

low MP + BP

→ covalently bonded molecules held by weak vdw forces

poor conductors due to lack of charged particles

properties of macromolecular crystal structures?

covalently bonded giant lattice

high MP

→ each atom has multiple strong covalent bonds

strength of length makes them rigid

example of macromolecular crystal structures?

diamond

→ carbon bonded to 4 others

graphite

→ carbon bonded to 3 others in flat sheets

→ unused electrons move in between layers and carry charge

how does lone pair repulsion affect bond angle?

decreases by 2.5 degrees for every lone pair

how is a bond angle formed?

electron pairs around an atom repel each other as far as possible

linear?

2 bonded

180 degrees

trigonal planar?

3 bonded

120 degrees

tetrahedral?

4 bonded

109 degrees

trigonal bipyramid?

5 bonded

3 120 degrees

2 90 degrees

octahedral?

6 bonded

90 degrees

trigonal pyramid?

3 bonded

1 lone

107 degrees

v shaped/bent?

2 bonded

2 lone

104.5

square planar?

4 bonded

2 lone

90 degrees

electronegativity?

power of an atom to attract negative charge towards itself within a covalent bond

how does electronegativity change?

increases a long a period

decreases down a group as shielding increases

decreases as atom size increases

how does a perm. dipole form?

2 polar bonded atoms have dif electronegativities

the more EN atom draws more of the negative charge towards itself, and away from the other

→ type of IM force

how does an induced dipole form?

if a molecule approaches an electron dense area, it repels the electrons to the back of the molecule, so the atom closest to the area is partially positive (the less EN one) and the further one negative

properties of VDW forces?

weakest, acts as an induced dipole

large Mr = stronger IM force

stronger in straight chained molecules

→ can line up and pack closer together

→ shortens distance over which the force acts making it stronger

properties of hydrogen bonding?

strongest

only between the lone pair in N, O + F and H from another molecule

high MP + BP

shown by a dashed line [ O|||||||||H ]