Bonding and Structure

Question 1

covalent bonding definition

Answer 1

electrostatic attraction between positive nuclei and the shared pair of negative electrons.

Question 2

list of metallic elements

Answer 2

Li, Be, Na, Mg, Al, K, Ca

Question 3

list of covalent molecular (diatomic) elements

Answer 3

H2, N2, O2, F2, Cl2

Question 4

list of discrete covalent molecular elements

Answer 4

P4, S8, C60 (fullerene)

Question 5

list of covalent network elements

Answer 5

B, C, Si

Question 6

list of monatomic elements

Answer 6

He, Ne, Ar… (noble gases)

Question 7

metallic bonding definition

Answer 7

electrostatic attraction between positive metal ions and a sea of delocalised negative outer electrons

Question 8

London dispersion forces definition

Answer 8

the weak forces between all atoms and molecules including monatomic elements. (weakest form of intermolecular bonding)

Question 9

strength of LDF

Answer 9

the strength of LDF is related to the number of electrons within an atom or molecule. The more electrons the stronger the LDF will be.

Question 10

difference between intermolecular and intramolecular forces

Answer 10

intramolecular- within molecules

intermolecular- between molecules

Question 11

metallic bonding properties

Answer 11

• conduct electricity when solid or liquid due to delocalised electrons.
• high density due to closely packed lattice structure
• usually high bp (lots of bonds to break)

Question 12

mp and bp of metallic elements trend

Answer 12

• increase across period because more electrons in outer shell, the stronger the metallic bond.
• decrease down a group because the additional filled electron shells weaken electrostatic forces between nuclei and delocalised electrons.

Question 13

monatomic elements properties

Answer 13

• exist as single atoms
• form no bonds due to full outer shell (no intramolecular bonding)
• do not conduct electricity because there are no free electrons.
• contain LDF

Question 14

covalent diatomic properties

Answer 14

-low mp/bp because it is the weak intermolecular forces which break between the molecules.

Question 15

covalent diatomic mp/bp trend

Answer 15

down the group, mp/bp increase because the strength of the LDF is increasing due to larger atoms with more electrons.

Question 16

Fullerene

Answer 16

• one of the three forms of carbon.
• smallest is C60, known as buckminsterfullerene
• does not conduct electricity as no free electrons.
• NOT A COVALENT NETWORK
• large molecule=strong LDF

Question 17

covalent network properties

Answer 17

• every atom linked to another by strong covalent bonds

- high mp/bp because lots of energy needed to break strong covalent bonds

Question 18

covalent network forms of carbon

Answer 18

DIAMOND
-tetrahedral structure
-does not conduct electricity (no free electrons)
-hardest natural substance (used for drills/cutting tools)
GRAPHITE
-layered structure with LDF between layers
-very soft (layers break away due to weak LDF)
-conducts electricity (delocalised electrons)

Question 19

allotrope

Answer 19

different form of same element

Question 20

discrete covalent molecular mp/bp

Answer 20

low because it is the weak intermolecular forces which break between molecules not covalent bonds within molecule

Question 21

noble gases mp trend

Answer 21

increases down the group as larger atoms with more electrons mean stronger LDF.

Question 22

3 types of Intramolecular bonding

Answer 22

1. covalent molecular (polar or non-polar)
2. Metallic
3. Ionic

Question 23

covalent bonding definition

Answer 23

• shared pair of electrons
• both nuclei try to pull electrons towards themselves
• creates a strong bond between the two atoms.

Question 24

pure/non-polar covalent bonding definition

Answer 24

when both atoms have an equal ‘pull’ on the shared electrons because they have the same electronegativity.
the electrons sit in the middle of the two nuclei.
Eneg difference 0.0-0.3

Question 25

polar covalent bond definition

Answer 25

- a bond formed when the shared pair of electrons in a covalent bond are not shared equally. - this is due to different elements having different electronegativities. - Eneg difference 0.4-2.5ish

Question 26

dipole moment

Answer 26

shows direction electrons are being pulled in

Question 27

the bonding continuum

Answer 27

a spectrum which starts at pure/non-polar covalent and ends at ionic

Question 28

how to work out if a molecule is polar or non-polar

Answer 28

1. is there a polar bond in the molecule (E difference>0.3) --> if not, non-polar 2. is the molecule symmetrical? yes=non-polar no=polar

Question 29

testing polarity

Answer 29

non-polar: charged rod does no attract or repel a stream of water. polar: charged rod attracts/repels stream of water.

Question 30

Ionic bond

Answer 30

- usually between metal and non-metal with a large E difference - forms a lattice of + and - ions - electrostatic force of attraction between positively and negatively charged ions - non metal (high eneg) gains electron to form negative ion - element with low eneg loses electron to form positive ion. - formula tells you ratio of ions

Question 31

increasing ionic character/polarity

Answer 31

increasing electronegativity difference

Question 32

3 types of intermolecular/ Van der Waals' forces

Answer 32

1. London Dispersion Forces 2. Permanent dipole-permanent dipole interactions 3. Hydrogen bonds

Question 33

what do intermolecular bonds dictate

Answer 33

melting/boiling points of molecules

Question 34

are intra or inter stronger?

Answer 34

intramolecular bonds are stronger (what holds atoms together)

Question 35

permanent dipole-permanent dipole

Answer 35

- occurs between polar molecules - the permanent dipole in one molecule is attracted to the permanent dipole of another - higher mp/bp than just LDF because pdp-pdp are stronger and take more energy to break.

Question 36

what is needed for a fair comparison between the mp/bp of a polar and non-polar molecule

Answer 36

similar formula mass

Question 37

polar or non-polar if only has LDF

Answer 37

non-polar

Question 38

polar or non-polar if molecule has LDF and pdp-pdp

Answer 38

polar

Question 39

hydrogen bonding

Answer 39

- strongest intermolecular bonding - occurs between molecules where there is an atom of H joined to an atom of N,O,F. - higher mp/bp as they are held most tightly together. - extreme case of pdp-pdp due to very large difference in electronegativity

Question 40

properties related to intermolecular forces: melting and boiling points

Answer 40

stronger bonds (pdp-pdp/hydrogen) require more energy to break as molecules are held more tightly together.

Question 41

viscosity

Answer 41

how thick/gloopy a liquid is

Question 42

increasing viscosity trend

Answer 42

more OH groups=more H bonding=molecules are held more tightly=more viscous

Question 43

miscibility

Answer 43

how well liquids mix together | miscible liquids mix thoroughly without any visible boundary

Question 44

why are some liquids immiscible

Answer 44

if one is polar, other is non-polar; unable to bond to one another

Question 45

what molecules will mix well with water

Answer 45

polar molecules

Question 46

why does 'like dissolve like'

Answer 46

due to attraction between the charges in each compound | polar substance+polar solvent-->soluble

Question 47

density

Answer 47

how tightly packed the particles are

Question 48

density of ice

Answer 48

ice is less dense than liquid water because hydrogen bonding between H20 molecules in ice gives a very open and expanded structure.

Question 49

what decides bonding type

Answer 49

difference in Eneg can decide bonding type | *ultimately properties of a substance which dictate bonding type*

Question 50

ionic bonding definition

Answer 50

electrostatic forces of attraction between positive and negative ions, usually between metal and non-metal.

Question 51

delocalised definition

Answer 51

delocalised electrons, in metallic bonding, are free from attachment to any one metal ion and are shared amongst the entire structure.

Question 52

dipole definition

Answer 52

an atom or molecule in which a concentration of positive charges is separated from a concentration of negative charges.

Question 53

isoelectronic

Answer 53

means having the same arrangement of electrons | Eg: Neon, Na+ and Mg2+

Question 54

lattice

Answer 54

a lattice is a regular 3D arrangement of particles in space. The term is applied to metal ions in a solid, and to positive and negative ions in an ionic solid.

Question 55

lone pairs

Answer 55

pairs of electrons in the outer shell of an atom which take no part in bonding.