Electronegativity and bond polarity Flashcards Preview

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Flashcards in Electronegativity and bond polarity Deck (8)
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What is Electronegativity?

Electronegativity is the measure of the attractions of a bonded atom for the pair of electrons in a covalent bond.


What changes when the bonded atoms are different elements?

- 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.
* in molecules of the same elements, electrons are shared evenly


How is Electronegativity measured?

- The Pauling scale has the Pauling electronegativity values and it can be used to compare E.N of elements
- Electronegativity depends of an element's position in the periodic table
- Nuclear charge increases across the periodic table and Atomic Radius decreases as you go up the table - Atomic radius has a bigger influence that nuclear charge
- Nitrogen, Oxygen, Fluorine and Chlorine are the most EN


How do Ionic bonds occur?

- When the EN difference is large, one bonded atom will have a much greater attraction and it will have gained control of the electrons


Bond types and the Electronegativity difference:

- Covalent = 0
- Polar covalent = 0-1.8
- Ionic = >1.8


Non-polar bonds

- In non polar bonds, electrons are shared equally.
- This happens when the bonded atoms are the same or if the bonded atoms have the same or similar EN
- Molecules of elements such as H2 where electrons are shared equally are called Pure Covalent bonds.
- Carbon and Hydrogen are a non-polar bond


Polar bonds

- A bond will be polar when the bonded atoms are different and have different electronegativity values, resulting in a polar covalent bond
- A bond becomes polarised with one atom having a slightly positive charge and the other have a slightly negative charge
- This separation of opposite charges is called a dipole
- Dipole in polar covalent bonds are permanent


Polar Molecules

- Multiple polar bonds may reinforce the polarity and make the molecule as a whole more polar - this happens in shapes with lone pairs
- Or they may oppose each other and cancel each other out thus becoming non polar