bonding

Question 1

what is metallic bonding?

Answer 1

strong attraction between positive ions and negative sea of electrons

Question 2

what are the properties of metals?

Answer 2

● good conductors of electricity

● good conductors of heat

● malleable

● ductile

● strong

● high melting point

Question 3

why are metals a good conductor of electricity?

Answer 3

delocalised elections can move through structure to carry the charge

Question 4

what does malleable mean?

Answer 4

can be beaten into shape

Question 5

what does ductile mean?

Answer 5

can be pulled into thin wires

Question 6

what does the strength of a metallic bond depend on?

Answer 6

● charge of ion ↑

● size of ion ↓

Question 7

why do metals have high melting points?

Answer 7

lots of energy required to overcome strong metallic bonds

Question 8

smaller ions will attract electrons…

Answer 8

more strongly as they are closer to nucleus

Question 9

if nuclear charge is bigger…

Answer 9

stronger attraction

Question 10

if there are more delocalised electrons…

Answer 10

more forces of attraction

Question 11

what is ionic bonding?

Answer 11

● electrons are transferred

● metal and non metal

Question 12

what is the ionic bonding structure?

Answer 12

● giant ionic lattice

● held together by strong electrostatic forces of attraction between oppositely charged ions

Question 13

what are the properties of giant ionic lattices?

Answer 13

● electrical conductivity

● shatters easily / brittle

● high melting point

Question 14

when are ions free to move in giant ionic lattices?

Answer 14

● when molten or aqueous ions are free to move and can conduct electricity

● when solid ions are not free to move and cannot conduct electricity

Question 15

explain strength in giant ionic lattices

Answer 15

● shatters easily / brittle

● any disruption to structure that makes positive ions or negative ions align will cause them to repel and shatter

Question 16

explain melting point in giant ionic lattices

Answer 16

● high

● strong electrostatic forces of attraction between oppositely charged ions

● force acts in all directions

Question 17

what does the strength of an ionic bond depend on?

Answer 17

● the larger the charge of ion, the stronger the attraction

● the smaller the ion, the stronger the attraction

Question 18

what is covalent bonding?

Answer 18

● shared pair of electrons

● strong

Question 19

what are properties of simple covalent molecules?

Answer 19

● melting point and boiling points are low

Question 20

what is the orbital theory?

Answer 20

covalent bonds are formed when orbitals, each containing 1 electron, overlap

Question 21

what is the octet rule?

Answer 21

● tendency to prefer 8 electrons in outer shell

● we do not consider p and f electrons

● only s and d are involved

Question 22

what is coordinate bonding?

Answer 22

● in most covalent bonds, each atom provides 1 electron

● but in some bonds, one atom provides both electrons

● shared pair of electrons but both electrons come from same atom

● have exactly same strength and length as ordinary covalent bonds once they are formed

Question 23

what are coordinate bonds represented by?

Answer 23

● →

● points towards atom accepting bond

Question 24

what is electronegativity?

Answer 24

the power of an atom to attract the electron density in a covalent bond towards itself it

Question 25

what are the factors affecting electronegativity?

Answer 25

● nuclear charge - more protons, stronger attraction between nucleus and bonding pair of electrons ● atomic radius - closer to the nucleus, stronger attraction between nucleus and bonding pairs of electrons ● shielding - less shells of electrons between the nucleus and the electrons less shielding (less repulsion), stronger attraction between nucleus and bonding pair of electrons

Question 26

what is the trend of electronegativity down a group?

Answer 26

● decreases ● nuclear charge increases, but atomic radius increases and more shielding ● therefore, less attraction between nucleus and bonding pair of electrons

Question 27

what is the trend of electronegativity across a period?

Answer 27

● increases ● nuclear charge increases, but atomic radius decreases and shielding stays the same ● therefore, stronger attraction between nucleus and bonding pair of electrons

Question 28

explain electronegativity in bonds between identical atoms

Answer 28

● electrons are shared equally ● no difference in electronegativity ● non polar

Question 29

explain electronegativity in bonds between different atoms

Answer 29

● different electronegativity ● one will pull the electrons closer to its end ● it will have a slight negative charge (δ⁻) ● other will have slight positive charge (δ⁺) ● leads to a charge difference called a dipole ● dipoles can be permanent ● greater the difference in electronegativity, the greater the polarity of the bond

Question 30

what are some elements with high electronegativity?

Answer 30

● O ● F ● N ● Cl

Question 31

what is polarity?

Answer 31

about unequal sharing of electrons between atoms that are bonded covalently

Question 32

how is bond polarity represented?

Answer 32

an arrow with a line at the end pointing to more electronegative atom

Question 33

explain non polar molecules

Answer 33

● they take into account all of the dipoles across the bonds of molecule ● for molecules that are symmetrical, dipoles of any bond within the molecule can cancel out

Question 34

explain polar molecules

Answer 34

● not all molecules containing polar bonds are polar overall ● if bond dipoles cancel each other the molecule isn't polar ● if there is a 'net dipole' the molecule will be polar

Question 35

is the molecule NH3 polar?

Answer 35

yes, shape of molecules means the dipoles do not cancel each other out

Question 36

is the molecule CCl4 polar?

Answer 36

no, although it contains polar bonds the molecules is symmetrical so the dipoles cancel out

Question 37

what do intramolecular bonds affect?

Answer 37

chemical bonds

Question 38

what do intermolecular forces affect?

Answer 38

physical properties

Question 39

what are the 3 types of forces between molecules?

Answer 39

● van der waals forces: act between all atoms and molecules ● dipole-dipole forces: act only between certain types of molecules ● hydrogen bonding: acts only between certain types of molecules

Question 40

explain van der waal forces

Answer 40

● as electrons are constantly moving an instantaneous dipole can occur in an atom or molecule that isn't polar ● this is where electron density shifts to one end of the molecule ● when instantaneous dipole comes close enough to another molecule it induces a new dipole in neighbouring molecule ● now also polar, the 2 are attracted to each other

Question 41

what affects strength of van der waal forces?

Answer 41

● number of electrons ● more electrons means the stronger the instantaneous dipole will be

Question 42

explain boiling point and van der waal forces

Answer 42

● electrons increase ● van der waal forces increase ● boiling point increases

Question 43

explain dipole-dipole forces

Answer 43

● polar molecules have permanent dipoles ● molecule will always have a negatively and positively charged end ● forces between two molecules that have permanent dipoles are called permanent dipole - dipole forces ● δ+ end of the dipole in one molecule and the δ- end of the dipole in a neighbouring molecule are attracted towards each other

Question 44

explain boiling point and dipole-dipole forces

Answer 44

extra attraction between dipoles means more energy must be put in to separate molecules so you get a higher boiling point than expected for a given mass

Question 45

explain hydrogen bonding

Answer 45

● force not bond ● same characteristics as covalent bond and dipole-dipole forces ● 1/10 strength of regular covalent bond ● only occurs when hydrogen is bonded covalently to fluorine, nitrogen or oxygen ● hydrogen has large charge density (small) and F, N and O are highly electronegative ● bond is polarised so that H of one molecule forms a weak bond with F, N or O of another molecule ● often attracted to lone pairs on O and N