Electronegativity + Polarisation

Question 1

Electronegativity

Answer 1

• ability of an atom to attract the bonding electrons in a covalent bond
• measured using pauling scale
• more electronegative elements have higher nuclear charges and smaller atomic radii
• increases across periods and up the groups

Question 2

covalent bonds

Answer 2

• bonding electrons sit in orbitals between 2 nuclei sp either have similar or identical electronegativity
• electrons sit midway between 2 nuclei so are non polar
• covalent bonds in homonuclear idiatomic (atoms that have equal EN) gases are non-polar so electrons are equally attracted to both nuclei

Question 3

polar

Answer 3

• if bond is between 2 atoms with dif EN the bonding electrons will be pulled towards more electronegative atom so electrons are spread unevenly so there’s a charge across bond making it polar
• greater difference in en greater shift in electron density so more polar the bond is

Question 4

Bonds

Answer 4

• single elements like diatomic gases are purely covalent so difference in en = 0 so arranged evenly
• higher difference in en more ionic bonding

Question 5

polar bonds don’t always make polar molecules

Answer 5

• polarity depends on shape and polarity of its bonds
• polar molecule has overall dipole caused by presence of permanent change across molecule
• simple molecule the polar bond gives the whole molecule a permanent dipole = polar molecules
• more complicated molecules have several polar bonds so if their arranged and point in opposite directions they’ll cancel each other out so are non-polar
• if polar bonds point in same direction are polar