Electronegativity and Polarity Flashcards
What is electronegativity and how is it measured
The ability of an atom in a covalent bond to attract the bonding pair of electrons. It is measured using Pauling’s electronegativity values
How does electronegativity change across periodic table
Increases across period up to group 7 and decreases down group
Which is the most electronegative element
Fluorine
Three factors affecting electronegativity
-nuclear charge
-atomic radius
-shielding
How does nuclear charge affect electronegativity
-more protons means stronger electrostatic force of attraction between nucleus and bonding pair of electrons, greater electronegativity
How does atomic radius affect electronegativity
Smaller the atomic radius the closer the nucleus to the bonding pair meaning stronger force of electrostatic attraction between the two, greater EN
How does shielding affect electronegativity
Less shells of electrons between the nucleus and bonding pair of electrons means less shielding so less repulsion meaning stronger force of attraction
Why does electronegativity decrease down group
As atomic radius increases and more shielding so less attraction between nucleus and bonding pair which outweighs the increase in nuclear charge
Why does electronegativity increase across period
Atomic radius decreases and nuclear charge increases so stronger force of attraction between nucleus and bonding pair, electrons added to same shell so shielding does not increase significantly
How does atomic radius change down group and across period
-increases down group
-decreases across period
What is a non-polar bond
Bond formed when electrons are shared equally between two atoms(dif in electronegativity between the two atoms must be very small or zero)
What is a polar bond
Bond formed when a bonding pair of electrons are not shared equally, due to difs in electronegativity the shared electrons are pulled towards atom with higher electronegativity by greater amount
Why do polar bonds have a positive and negative pole
-delta negative side has slight excess of negative charge and delta positive side is where electrons are less strongly attracted
What is a purely covalent bond
When the electron pair is shared equally between two atoms with the same electronegativities
What is purely ionic bonding
Giant lattice of spherical ions held together by electrostatic forces of attraction, with the electron transfer from reactive metal to highly electronegative non-metal so large difference in electronegativity
What is polarisation in ionic bonding
When small and highly charged (high charge density) cations distort electron clouds of anions causing partial covalency as electrons are attracted to this cation
What is a polar covalent bond
Bond in which the atoms have slightly different electronegativities so an unequal attraction for electrons so sharing is unequal
Order of type of bonding from atoms with very different electronegativities so the same electronegativity
-purely ionic (very different electronegativity)
-ionic bonding with polarisation
-polar covalent bonding
-purely covalent (identical electronegativity)
What is Pauling’s electronegativity scale and what is the value for fluorine
-from 0 to 4 for electronegativity with fluorine being the most electronegative with a value of 4.0
When does a bond become ionic
When the difference in electronegativity between the two atoms is large enough for the more electronegative element to remove electrons completely from the less electronegative atom
What is a polar molecule
Molecule that contains polar bonds which do not cancel each other out so the whole molecule is polar and has a positive and negative electric pole called a dipole
Which molecules have an overall dipole moment
Polar molecules in which their polar bonds do not cancel each other out so there is an overall twisting effect
