Electronegativity Flashcards
define electronegativity?
the ability of an atom to attract the pair of electrons in a covalent bond.
What affect electronegativity?
nuclear charge
atomic radius
electron shielding
What is the most electronegative element?
Fluorine - largest nuclear charge
small atomic radius
How do you get a non polar bond?
both bonding elements have the same electronegativities
When do you get a polar bond?
Bonding atoms have different electronegativities.
What is the strongest type of intermolecular force?
Hydrogen bonding
What is the weakest type of intermolecular force?
induced dipole dipole / van der waals forces
Describe van der waals’ forces of attraction?
There is a random movement of electrons which leads to a temporary uneven distribution of electrons. This creates a dipole which induces a dipole in its neighbouring molecules.This leads to a temporary dipole dipole attraction.
Are van der waals forces stronger in smaller or larger molecules?
Larger because there are more electrons
Describe permanent dipole dipole attraction?
- occurs in polar molecules only
-Polar molecules are attracted to each other - they are stronger than induced dipole dipole.
-forces of attraction between dipoles and those of neighbouring molecules.
What conditions are needed for hydrogen bonding to occur?
O-H
N-H
F-H
because O N and F are highly electronegative, H nucleus is left exposed.
There is a strong force of attraction between H nucleus and lone pair of electrons on O,N,F
Why is ice less dense than liquid water?
in liquid water - hydrogen bonds constantly break and reform as molecules move about
in ice - the hydrogen bond holds the molecules in fixed positions - this makes them slightly further apart in liquid water.
