Molecular shape and Bonding

Question 1

what is a non- polar covalent bond ?

Answer 1

_ Similar electronegativity

Question 2

what is a polar covalent bond ?

Answer 2

• have dipoles
• difference in electronegativity less than 2

Question 3

what are 3 properties of ionic compounds ?

Answer 3

• highly ordered crystal lattice
• conduct electricity when molten
• high bp

Question 4

what are electropositive elements ?

Answer 4

• elements with low ionisation energy (outer e- easily removed)

Question 5

what are electronegative elements ?

Answer 5

• elements that readily acquire electrons

Question 6

what are the factors affecting lattice energy ?

Answer 6

• ionic radius
• ionic charge
• no of shells /sheilding

Question 7

How does ionic radius affect LE ?

Answer 7

• smaller ionic radius = greater attraction so higher LE

Question 8

How does ionic charge affect LE ?

Answer 8

• greater ionic charge = greater attraction so higher lE

Question 9

what is electronegativity ?

Answer 9

• the ability of an atom to pull bonding electrons towards itself

Question 10

what are degenerate orbitals ?

Answer 10

• have same energy level
• eg 2p orbitals

Question 11

why do electrons in degenerate orbitlas occupy empty ones first ?

Answer 11

• to minimise repulsion

Question 12

why is the 4s orbital filled before 3d ?

Answer 12

• it has a lower energy level

Question 13

what is a radial node ?

Answer 13

• region where there is zero probability of finding an electron

Question 14

what are 2 properties of 2p orbitals ?

Answer 14

• degenerate (same energy)
• each orbital is perpendicular to the other two

Question 15

what is the rule for molecular orbital theory ?

Answer 15

• number of AO = number of MO
• always get a bonding and anti-bonding MO

Question 16

what is a sigma bonding molecular orbital ?

Answer 16

• atomic orbitals of same phase sign overlap

Question 17

what is anti-bonding molecular orbital ?

Answer 17

• atomic orbitals of opposite phase sign overlap

Question 18

what is constructive combination ?

Answer 18

• wave function of e- are in the same phase

Question 19

what is destructive combination ?

Answer 19

• wave function of e- are in opposite phases

Question 20

what is the difference between anti bonding and bonding MO ?

Answer 20

• anti bonding has a node and no electrons
• anti - bonding is higher in energy

Question 21

What does end on overlap of 2p orbitals lead to ?

Answer 21

• sigma bonds

Question 22

what does side on overlap of p orbitals lead to ?

Answer 22

• pi bonds

Question 23

explain the hybridization of carbon for CH4 ?

Answer 23

• one e- from a 2s orbital is promoted to a spare p orbital
• makes 4 degenerate sp3 orbitals
• helps from 4 equivalent bonds

Question 24

How are C-H bonds formed in ethane ?

Answer 24

• overlap of sp3 and hydrogen s orbital

Question 25

How are C-C bonds formed in ethane ?

Answer 25

- overlap of 2 carbon sp3 orbitals

Question 26

what is the bond angle for sp3 hybrids ?

Answer 26

109.5

Question 27

how is the c-c double bond formed in ethene?

Answer 27

- sigma bond formed by overall of 2 carbon sp2 orbitals - Pi bond formed by side to side overlap of unhybridized p orbitals

Question 28

what is the bond angle and shape of sp2 ?

Answer 28

120 - trigonal planar

Question 29

what is the structure of ethyne ?

Answer 29

- triple bond between carbons - each c attached to a H

Question 30

What is bond angle and shape of sp orbital ?

Answer 30

- 180 - linear

Question 31

how many sigma and pi bonds are in a triple bond ?

Answer 31

2 pi bonds 1 sigma bond

Question 32

what is the shape + bonding in a methyl cation ?

Answer 32

- CH3 + - sp2 hybridisation - trigonal planar - 120

Question 33

what is the bonding in a methyl radical ?

Answer 33

-CH3* - sp2 hybridization - trigonal planar - 120

Question 34

what is the shape + bonding in a methyl anion ?

Answer 34

- three bonding pairs and 1 lone pair - sp3 hybridization - tetrahedral 109.5

Question 35

what is hybridisation of NH3 ?

Answer 35

- 3 bonding pairs 1 lone pair - sp3 orbitals - bond angle is 107

Question 36

How is the C-N bond formed ?

Answer 36

sp3 - sp3 overlap

Question 37

hybridisation of H20 ?

Answer 37

- sp3 oribitals - including lone pairs - 104.5

Question 38

What is the bonding in hydrogen halides ?

Answer 38

S-sp3

Question 39

Why is H-F bond stronger than HCI bond?

Answer 39

HF = 1s and 2sp3 orbital HCl = 1s and 3sp3 orbital CL bigger than F so less electron density in s-sp3 As size of X increases h-x bond gets weaker

Question 40

How does size of halide effect bond strength?

Answer 40

As size increases bond gets weaker + longer

Question 41

What are Van Der Waal forces ?

Answer 41

- Weak interactions caused by momentary changes in e- density

Question 42

What is an intermolecular bond?

Answer 42

- Between molecules

Question 43

What is an intramolecular bond?

Answer 43

- Within a molecule

Question 44

What is the order of bond strength?

Answer 44

electrostatic forces Ionic bonds > H bonds > permanent dipole - dipole > London forces

Question 45

What are the 2 conformations of alkanes?

Answer 45

- Staggered + eclipsed - eclipsed the H are closer together

Question 46

Is staggered or eclipsed conformation more stable ?

Answer 46

- staggered is more stable than eclipse , lower in energy

Question 47

what is torsional strain ?

Answer 47

- repulsion of proximate bonding electrons - only found in eclipse conformation

Question 48

what is steric strain ?

Answer 48

- atoms / groups too close to eachother so e - clouds repel - found in staggered or eclipsed

Question 49

what is angle strain ?

Answer 49

- deviation from ideal tetrahedral bond angle

Question 50

which conformation of cyclohexane is more stable ?

Answer 50

- chair conformation because no angular + torsional strain