6.2 Electronegativity and polarity Flashcards
What occurs in a covalent bond?
The nuclei of the bonded atoms attract the shared pair of electrons.
What happens in a covalent bond between the same element?
The bonded electron pair is shared evenly
What happens in a covalent bond between different elements?
The nucleus charges are different
The atoms may be different sizes
the shared pair of electrons may be closer to one nucleus than the other.
The shared pair of electrons may now experience more attraction from one bonded atoms than the other
What is electronegativity?
It is the attraction of a bonded atom for the apir of electrons in a covalent bond
What si teh Pauling scale used for?
To compare the electronegativity of the atoms of different elements
What do the Pauling electronegativity values depend on?
It depend on an elements position in the periodic table
How does electronegativity values increase?
The higher and the most to the right the element is the higher the electronegative value it has
Across the periodic table the nuclear charge ….. and the atomic radius …..
Across the periodic table the nuclear charge INCREASES and the atomic radius DECREASE
A large Pauling value indicates that the atoms of the element are …
Very electronegative
Which element has the highest Pauling value (and therefore is very electronegative)
Fluorine (4.0)
What group on the periodic table is not included int eh Pauling scale and why?
The noble gases are not included because they often do not form compounds
Which group contains the most electronegative atoms?
Non-metals
Which group contains the least electronegative elements?
Metals
What are the 3 bond types?
covalent
polar covalent
ionic
What is the electronegative difference in a covalent bond?
0
What is the electronegative difference in a polar covalent bond?
0 to 1.8
What is the electronegative difference in an ionic bond?
Greater than 1.8
What happens if the electronegativity difference is larger?
1 bonded atom will have a much greater attraction for the shared pair than the other bonded atoms.
What will an atom gain is it is more electronegative?
It will gain control of the electrons and the bond will therefore, be ionic rather than covalent
What are non-polar bonds?
It is when the bonded electron pair is shared equally between the bonded atoms
When will a bond be non-polar?
The bonded atoms are the same
or
The bonded atoms have the same or similar electronegativity
What is a pure covalent bond?
It is molecules with the same elements and the electron pair os shared equally
What are hydrocarbon liquids (such as hexane C6H14)?
They are non-solvent and do not mix with water
What happens in a polar bond?
The bonded electron pair is shared unequally between the bonded atoms
When will a bond be polar?
The bonded atoms are different
They have differnt electronegativity
What bond is formed in hydrogen chloride and why?
the chlorine is more electronegative than hydrogen and therefore it is more has attraction for the bonded pair of electrons than the hydrogen.
For this reson it is a polar covalent bond
The H-Cl is polarised, hwta does this mean?
the H-Cl is polarised with a small parcial positive charge H atom and small parical negative charge Cl atom
What is meant by dipole?
It is the seperation of opposite charges
What is ment by perament dipole?
A dipole in a polar covalent bond that doesn’t change
In what why does the shape of the molecule affect the dipole?
The dipoles may reinforce one anther to produce a larger dipole over the whole molecule, or cancel out if the dipoles act in opposite directions
What is the dipole of water and is it polar?
The dipole is going up and therefore it is polar
What is the dipole of CO2 and is it polar?
The dipoles cancel each other out and is, therefore, non-polar
What does a sodium chloride lattice form when it begins to dissolve in water and why?
It forms aqueous sodium a and chloride ions
water molecules attract Na+ and Cl- ions
The ionic lattice breaks down as it dissolves
Int the resulting solution water molecules surround the Na+ and the Cl-
What do you see as a sodium chloride lattice begins to dissolve in water?
Na+ ions are attracted towards O in water
Cl- ions are attracted towards H in water
