Electronegativity And Polarity Flashcards
What do the nuclei of bonded atoms do in a covalent bond?
They attract the shared pair of electrons.
What happens in molecules of elements?
The bonded electron pair is shared evenly.
Why may polarity change when molecules contain different elements?
3 reasons
The nuclear charges are different.
The atoms may be different sizes.
The shared pair of electrons may be closer to one nucleus than the other.
What do the shared pair of electrons from different elements in a molecule experience?
More attraction from one of the bonded atoms than the other.
What is electronegativity?
The attraction of a bonded atom for the pair of electrons in a covalent bond.
How is electronegativity measured?
Using the Pauling scale.
What are the Pauling electronegativity values based on?
The periodic table.
What is the pattern with the Pauling electronegativity values?
Electronegativity increases across and up the periodic table.
What will happen if the electronegativity difference is large?
The bond will be ionic as the more electronegative atom will have a mch greater attraction for the shared pair of electrons.
What is the electronegativity difference for covalent bonds?
0
What is the electronegativity difference for polar covalent bond?
0 to 1.8
What is thee electronegativity difference for an ionic bond?
Greater than 1.8
What happens in a non-polar bond?
The bonded electron pair is shared equally between the bonded atoms.
What makes a bond non-polar?
The bonded atoms are the same or the bonded atoms or the bonded atoms have the same or similar electronegativity.
What is meant by the term pure covalent bond?
The bonded atoms come from the same element and the electron pair is shared equally.
Which two elements form pure covalent bonds and have very similar electronegativity?
Carbon and hydrogen
What happens in a polar bond?
The bonded elecron pair is shared unequally between the bonded atoms.
What is a dipole?
The separation of opposite charges.
What is a permanent dipole?
A dipole in a covalent bond that does not change.
Is there only ever one polar bond?
No, molecules containing more than two atoms can have more than one polar bond.
What might happen if there is more than one polar bond in a molecule?
The dipoles may reinforce each other to create a larger dipole over the whole molecule, or cancel each other out if the dipoles act in opposite directions.
Give an example of a polar molecule.
H2O
In water, what do the two O-H bonds have?
A permanent dipole each.
What do the two dipoles do in water molecules?
They act in different directions but do not exactly oppose each other.
What is the charge of the oxygen atom in a water molecule?
Delta -
What is the charge of hydrogen in a water molecule?
Delta +
Give an example of a non-polar molecule?
CO2
What do the two C=O bonds have?
A permanent dipole.
What do the dipoles in CO2 do to each other?
They act in opposite directions and exactly oppress each other, making the molecule non-polar as the dipoles cancel each other out.
What is the overall dipole of a non-polar molecule?
0
