6.2 Electronegativity and polarity

define electronegativity

the attraction of a bonded atom for the pair of electrons in a covalent bond

why does the electronegativity of bonded atoms of different elements change

1) nuclear charges are different. 2) the atoms may be different sizes. 3) the shared pair of electrons may be closer to one nucleus than the other

describe the Pauling scale

used to compare the electronegativity of atoms of different elements

what charge does an atom with larger electronegativity have

partially negative

what charge does an atom with smaller electronegativity have

partially positive

the bond type if the electronegativity is 0

covalent

the bond type if the electronegativity is 0-1.8

polar covalent

the bond type if the electronegativity is over 1.8

ionic

what type of elements have the most electronegative atoms

the non metals N, O, F, Cl

what type of elements have the least electronegative atoms

the group 1 metals Li, Na, K

define non-polar bond

where the bonded electron pair is shared equally between the bonded atoms

define pure covalent bond

the bonded atoms come from the same element and the electron pair is shared equally

define polar bond

the bonded electron pair is shared unequally between the bonded atoms

define dipole

the separation of opposite charges

define permanent dipole

a dipole in a covalent bond which does not change caused by a difference in electronegativities of the two atoms

explain why CO2 is non-polar

1) each C=O bond has a permanent dipole. 2) the 2 dipoles act in opposite directions and exactly oppose each other. 3) overall the dipoles cancel out. 4) the overall dipole is 0

explain why H2O is polar

1) each O-H bond has a permanent dipole. 2) the 2 dipoles act in different directions but do not oppose each other. 3) overall O is partially negative, H is partially positive

explain how NaCl dissolves in water

1) water molecules attract sodium ions and chloride ions. 2) the ionic lattice breaks down as it dissolves. 3) water molecules surround the sodium ions and chloride ions. 4) sodium ions are attracted toward the oxygen atoms and chloride ions are attracted towards the hydrogen atoms