bonding notes

Question 1

Metallic Structure and Bonding

Answer 1

giant metallic lattice
strong electrostatic attraction between positive metal ions and delocalised electrons

Question 2

The bonding in Magnesium is stronger than in Sodium because:

Answer 2

Mg has a greater charge of 2+

Mg has twice as many electrons in the sea of delocalised electrons

Mg ions are smaller, greater charge density

therefore, attraction between Mg2+ ions and delocalised electrons is stronger

Question 3

properties of metals:

Answer 3

conductivity:
electrical and thermal conductors delocalised electrons to transfer current

strength:
strong electrostatic attraction between positive metal ions and sea of delocalised electrons

malleable and ductile:
hammered into shape
pulled into wires
rows of metal ions can slide past one another

melting and boiling points:
strength of metallic bonds;
stronger they are;
higher mp and bp

Question 4

Covalent Structure and Bonding

Answer 4

macromolecular and simple
molecular

A covalent bond is a shared pair of electrons between two atoms

Question 5

macromolecular structures:

Answer 5

silicon
carbon
silicon oxide

Question 6

Diamond:

Answer 6

Each C has 4 covalent bonds
tetrahedral shape
very high mp
very hard
non conductor (no delocalised electrons)

Question 7

graphite:

Answer 7

layers with 3 covalent bonds to each C atom
each C has a delocalised electron
layers held together by weak intermolecular forces
soft layers can slide over one another
conductor has delocalised electrons
mp high

Question 8

forces and properties of simple molecular structures;

Answer 8

IMFs act between molecules

melting causes breaking of IMFs

IMFs weaker than covalent bonds

low MP

Question 9

Ionic structure and bonding:

Answer 9

Giant ionic lattice

strong electrostatic attractions between oppositely charged ions

Question 10

Physical and structural properties of ionic compounds:

Answer 10

high mp and bp

electrical conductivity - aqueous or molten

brittle and shatter easily

Question 11

ammonium:

Answer 11

NH4+

Question 12

hydroxide

Answer 12

OH-

Question 13

nitrate

Answer 13

NO3-

Question 14

nitrite

Answer 14

NO2-

Question 15

hydrogencarbonate

Answer 15

HCO3-

Question 16

Chlorate(I)

Answer 16

CIO-

Question 17

Chlorate(v)

Answer 17

CIO3-

Question 18

carbonate

Answer 18

CO32-

Question 19

sulfate

Answer 19

SO42-

Question 20

sulfite

Answer 20

SO32-

Question 21

dichromate

Answer 21

Cr2O72-

Question 22

phosphate

Answer 22

PO43-

Question 23

Coordinate bonds

Answer 23

A coordinate bond is a shared pair of electrons which have both come from the same atom

Question 24

Define electronegativity

Answer 24

the ability of an atom to attract electron density from a covalent bond

Question 25

The factors which determine how electronegative an element are:

Answer 25

nuclear charge the atomic radius the shielding

Question 26

why is fluorine the most electronegative?

Answer 26

as you go UP groups - electronegativity INCREASES because radius and amount of shielding DECREASES as you move ACROSS a period - electronegativity INCREASES beaches the nuclear charge INCREASES and the radius DECREASES

Question 27

what are the three types of intermolecular forces?

Answer 27

induced dipole dipole (van der waals forces) permanent dipole dipole hydrogen bonding

Question 28

when does hydrogen bonding occur?

Answer 28

occurs between H and lone pair on either: N, O, F strongest IMF

Question 29

how does hydrogen boding arise?

Answer 29

very large difference in electronegativity between Oxygen (NOF) and H creates a dipole on the O-H bond lone pair on oxygen atom in one molecule strongly attracts a partially positive H on a different molecule

Question 30

when do permanent dipole dipole forces occur?

Answer 30

between polar molecules generally weaker than hydrogen bonding

Question 31

how do permanent dipole dipole forces arise?

Answer 31

difference in electronegativity leads to bond polarity dipoles don’t cancel out, therefore the molecule has an overall permanent dipole there is an attraction between s+ on one molecule and s- on another

Question 32

when do induced dipole dipole forces (VDWs) occur?

Answer 32

occurs between all molecules but most important for non polar molecules generally the weakest force but can be stronger than hydrogen bonding and permanent dipole dipole if molecule is large enough = lots of electrons

Question 33

how do induced dipole dipole occur?

Answer 33

Random movement of electrons in one molecule leads to… Uneven distribution of electrons, creating a… Temporary dipole in one molecule… Induces dipole in a neighbouring molecule Dipoles attract

Question 34

importance of hydrogen bonding

Answer 34

ice: less dense than water because the hydrogen bonds in ice hold the molecules further apart proteins: they’re held in their complex 3D shapes by hydrogen bonds the shape of a protein is vital for its function DNA: carries all genetic information of living things the two strands in the double helix are held together by hydrogen bonds strong enough to hold together and weak enough to allow strands to separate for semi conservative replication

Question 35

physical properties in period 3 elements mp and bp (na to mg to al)

Answer 35

increases strong attraction between cation and delocalised electrons charge on ion increases size decreases more delocalised electrons

Question 36

physical trends in period 3 elements : silicon

Answer 36

macromolecular to melt Si many strong covalent bonds must be broken which requires a large amount of energy therefore Si has the highest MP

Question 37

physical trends in period 3 elements : P, S, Cl

Answer 37

simple molecular P4 S8 Cl2 covalent bonding between atoms VDWs forces between molecules weak forces S8 slightly highest MP and BP = greater electrons S8>P4>Cl2

Question 38

physical trends in period 3 elements : Ar

Answer 38

monoatomic no bonding weakest vdws between atoms least amount of e- smallest