VSEPR and VSEPR and PolarityPolarity

Since all atoms have different Since all atoms have different electronegativities, a “electronegativities, a “ ” for the ” for the electrons in a bond begins when atoms bond.electrons in a bond begins when atoms bond.

When an atom bonds with another one of When an atom bonds with another one of itself (example F-F), the difference in itself (example F-F), the difference in electronegativity is electronegativity is . This is known as . This is known as

covalent or covalent or covalent bond.covalent bond.

When an atom bonds with different atoms, When an atom bonds with different atoms, they can be they can be or _________ covalent bonds, or _________ covalent bonds, depending on the differences in depending on the differences in electronegativities. electronegativities.

Tug of war

zero

nonpolarpure

polar nonpolar

What happen when the What happen when the electronegativity isn’t equalelectronegativity isn’t equal When the difference in electronegativity is When the difference in electronegativity is

, an electron is , an electron is and and bonding results. bonding results.

When the difference in electronegativity is When the difference in electronegativity is ______ ____________, the , the electrons are __________ ____________ and electrons are __________ ____________ and

bonding results. bonding results.

largetransferre

dionic

very sharedequally

small (<0.5)nonpolar

When the difference in electronegativity is When the difference in electronegativity is , there is , there is sharing. sharing.

Resulting in a Resulting in a covalent. covalent. As a result, the electrons spend more time As a result, the electrons spend more time

around the around the electronegative ( electronegative () atom, which makes it ) atom, which makes it

slightly slightly . The weaker atom . The weaker atom becomes slightly becomes slightly ..

This results in the polar bond being a This results in the polar bond being a – two poles – two poles

moderateunequa

lpolar

more strongernegativepositive

dipole

Polarity of MoleculesPolarity of Molecules Overall, molecules can be Overall, molecules can be or or

, depending on the results of the , depending on the results of the molecular “molecular “ ..”” If the VESPR shape makes it a If the VESPR shape makes it a molecule molecule

then the result is then the result is .. If VESPR shape makes it a If VESPR shape makes it a molecule molecule

then the result is then the result is .. Let’s look at HLet’s look at H22OO Water is Water is , , because its shape isbecause its shape is

Tug of war

non-polarpolar

nonpolar

polar

polar

symmetrical

asymmetrical

Asymmetrical (bent)

So, what does this mean So, what does this mean to us?to us?

To determine if a molecule is polar or To determine if a molecule is polar or not, ask yourself:not, ask yourself: Are there dots on the central atom? If Are there dots on the central atom? If

__________________ , it is automatically __________________ , it is automatically __________________. If not, then ask yourself:__________________. If not, then ask yourself:

Are all the elements around the central Are all the elements around the central atom the same (or are the two atoms the atom the same (or are the two atoms the same in the case of the two atom linear same in the case of the two atom linear molecules)? If __________________, It is molecules)? If __________________, It is __________________.__________________.

yespolar

yes NONPOLAR

Let’s look at HLet’s look at H22OO

Water has _____________ which makes its Water has _____________ which makes its shape __________________, so this would shape __________________, so this would make water __________________.make water __________________.

  Ability of a substance to dissolve is based Ability of a substance to dissolve is based on polarity … _____________ dissolves on polarity … _____________ dissolves _____________._____________.

So, _____________ dissolves polar and So, _____________ dissolves polar and _____________ dissolves non-polar._____________ dissolves non-polar.

Water is polar, so it dissolves Water is polar, so it dissolves _____________ substances_____________ substances

dots

asymmetricalpolar

likelike

polar

polar

nonpolar

ForcesForces

Ionic and covalent bonds are called Ionic and covalent bonds are called

(within molecules)(within molecules)

– – between molecules – between molecules – also called also called forces forces – –

Intermolecular forces are Intermolecular forces are than intramolecular forces. than intramolecular forces.

intramolecular

Intermolecular WEAKVan der Waals always weaker