Electronegativity and bond polarity

Question 1

Electronegativity definition?

Answer 1

The ability of an atom to attract the bonding electrons in a covalent bond
- the further up and right you go in periodic table (exc noble gases) the more electronegative element is…
- decreases down group
- increases from left to right across period
- F the most electronegative

Question 2

Electronegativity measured using…

Answer 2

The Pauling Scale

Question 3

The bigger the diff in electronegativity…

Answer 3

the more ionic the compound will be - diff of 0 - purely covalent

Question 4

Distribution of electron density?

Answer 4

• if 2 atoms of same element bonded tgt by overlap of orbitals - distribution of electron density between 2 nuclei = symmetrical as - ability of each atom to attract bonding pair of electrons is identical
• contour lines (of electron density diagram) = likelihood that bonding electron will fall within contour at given time

Question 5

Polar covalent bonds?

Answer 5

if atoms bonded tgt r from diff elements w diff electronegativities - distribution of electron density NOT symmetrical ab 2 nuclei
E.G. HCl
- since electron density higher around Cl atom - that end of molecule has acquired slightly negative charge (delta-)
- other end of molecule carries slightly positive charge (delta+)
- can represent using an arrow to show electron drift
- can be thought of as being between 2 ideals on bonding types - pure covalent & pure ionic so - polar bonds: covalent bond w some degree of ionic character

Question 6

If covalent bond between 2 atoms w diff electronegativities?… (step-by-step)

Answer 6

• bonding electrons wil be pulled towards the more electronegative atom
• causes electrons to be spread unevenly so - charge across bond (each atom has partial charge - +/-) so bond = polar
• in polar bond: diff in electronegativity causes a dipole
• the greater the diff in electronegativity, the greater the shift in electron density + the more polar the bond
• bonds r polar if diff in electronegativity > 0.4

Question 7

Dipole definition?

Answer 7

a diff in charge between 2 atoms caused by a shift in electron density in the bond
- the drift of bonded electrons towards more electronegative - separation of charge aka dipole
- each of bonds in a molecule has its own dipole associated w it
-if dipoles reinforce one another: polar
- if dipoles cancel out (symmetrical) one another: non polar

Question 8

Drawing polar bonds?

Answer 8

• shared pair of electrons (dot and cross on top & bottom of bond) pulled towards the more electronegative atom/if not polar: sit in middle
• *hydrocarbons not polar
• arrow from + to - (can use to determine whether charges cancel our or not)
• if polar bonds point in opp directions - cancel out so - non-polar
• if polar bonds point in same direction - polar molecule