Polarity Flashcards
how to assign formal charges with covalent bonds
shared e- are divided equally between the two atoms
doesn’t take polarity into account
how to observe polarity of a molecule
place in an electric field - molecule will align
what is bond polarity caused by?
differences in electronegativity
electronegativity
intrinsic ability of an atom to attract electrons in a covalent bond
why does the electronegativity increase across the periodic table?
more protons (nuclear charge increases)
why does the electronegativity decrease down the periodic table?
more shells - electrons are further from the nuclear
electronegativity of noble gases
close to zero
no need to attract an e- as shell is already full
why is CH non-polar?
C and H have similar electronegativities
why is CF polar?
electron pair attracted towards F due to higher electronegativity
C has partial positive charge
F has partial negative charge
how is the bond polarisation indicated?
by arrow (electrons move in direction of arrow)
negative to positive
inductive effect
shifting of electrons in a bond in response to the electronegativity of nearby atoms
what determines overall molecular polarity?
sum of contributions from individual bonds and lone pairs (net molecular dipole)
dipole moment
measure of polarity due to separation of ‘centres of mass’ of positive and negative charges in a molecule
unit for dipole moment
Debye (D)
dipole moment equation
μ = qr
dipole moment = charge x distance
