Electronegativity and bond polarity Flashcards
What is electronegativity?
The ability of an atom to attract the bonding electrons in a covalent bond
What is a dipole?
A separation in electrical charge so that one atom of a polar covalent bond, or one end of a polar molecule, has a delta positive charge and the other side has a delta negative charge
(a molecule with a definite + and - side)
How are dipoles induced?
- random motion of electrons in a molecule
- temporary asymmetry in electron arrangement causes one area of the molecule to become slightly negative and one area slightly negative
- this induces a dipole on a neighbouring molecule
- the induced dipole further induces dipoles on neighbouring molecules
How does a greater number of electrons affect London forces within a molecule?
- the greater the the asymmetry
- larger instantaneous and induced dipoles
- greater induced dipole-dipole interactions
- so stronger London forces
Why does iodine have a higher melting point than chlorine?
- more electrons
- larger temporary dipole
- greater instantaneous dipole-dipole forces
- stronger attractive forces between molecules
- more energy required to overcome the forces
What two factors affect the strength on London forces?
- number of atoms
- contact area of a molecule
Which has stronger London forces; branched or unbranched molecules?
Unbranched
Explain why unbranched molecules have stronger London forces than branched molecules
- greater CONTACT AREA between molecules
- STRONGER induced dipoles develop
- therefore greater London forces
What is used to measure electronegativity of atoms?
The Pauling scale
What is the trend of electronegativity within the periodic table?
It increases across and up the periodic table
Which is the most electronegative element?
Fluorine
Which 4 elements are highly electronegative?
Fluorine, chlorine, nitrogen, oxygen
Which trend has the same trend as electronegativity?
1st Ionisation energy
Which element is the least electronegative?
Caesium
