S2.2 Covalent Model - Bonds & Polarity

Question 1

Dative covalent/ coordination bond

Answer 1

occurs when both e- are donated from one atom

donor must have a lone pair of electrons it can donate

acceptor must have space for an electron pair

Question 2

sigma bond

Answer 2

formed when two atomic orbitals (one from each bonding atom) combine head on orientation to form a new molecular orbital
=> axial/end to end overlap
=> creates dense electron cloud

Question 3

pi bond

Answer 3

formed by the sideways overlap of two p orbitals orbitals of two different atoms
=> when orbitals are parallel

Question 4

Pi bonds in resonance

Answer 4

have big area of overlap in which electrons can move around

Question 4

Sigma vs pi bonds

Answer 4

sigma bonds are stronger
= head on overlap makes them stronger

(proven by enthalpy, increase of c-c bond to c=c bond)

Question 5

electronegativity

Answer 5

a measure of the attraction that an atom has for bonded electrons

Question 6

pure covalent bond

Answer 6

when 2 atoms bonded by a covalent bond have the same electronegativity value thus the electrons are equally shared

Question 7

non polar covalent bond

Answer 7

slight difference in EN between two atoms

Question 8

polar covalent bond

Answer 8

two atoms with different EN values resulting in an unequal sharing of electrons

Question 9

electron density cloud

Answer 9

shows where electrons are likely to be shaped by an atoms EN

Question 10

how a polar covalent bond arises

Answer 10

1. two atoms with different EN values form a covalent bond
2. there will be an unequal sharing of electrons -> electrons lie closer to one atom
3. atom with higher EN will take greater share of electrons

Question 11

Dipole-Dipole Moment

Answer 11

The two seperated opposite electric charges, part. + and part. - existing in a polar bond

Question 12

Dipole

Answer 12

partial charges associated with polar bonds

Question 13

how ionic bondig arises

Answer 13

• forms due to large EN difference between atoms involved
• electrons are transferred from an atom with lower EN to atom with higher EN
• as electrons transferred = ions are formed

Question 14

bonding continuum

Answer 14

used to help determine if a compound is pure covalent, polar covalent or ionic
* based on fluorine
* goes up to 4.0

Question 15

1.

Bonding continuum - ionic

Answer 15

≥1.8

Question 16

Bonding continuum - non polar covalent

Answer 16

! weakly polar !
0.1 to 0.4

Question 16

non polar molecule - bond shape

Answer 16

• bonds arranged symmetrically
• partial charges cancel out

Question 17

bonding continuum - pure covalent

Answer 17

0

Question 18

Bonding continuum - polar covalent

Answer 18

0.5 to 1.7

Question 19

polar molecule - bond shape

Answer 19

• bonds arranged asymmetrically
• partial charges do not cancel out

Question 20

polar

Answer 20

molecules containing a polar bond/asymmetrical arrangement of polar bonds that therefore have an overall dipole

Question 21

non polar

Answer 21

molecules containing no polar bonds/a symmetrical arrangement of polar bonds that therefore have no overall dipole