Shape and Polarity

Question 1

What is the VSEPR theory

Answer 1

Valence shell electron pair repulsion
-shape of molecule depends on number of valence shell e- pairs around the central atom
-pairs of e- in the valence shell repel one another since their electron clouds are negatively charged

Question 2

What are the bond shapes

Answer 2

-linear
-V shaped
-trigonal planar
-tetrahedral
-trigonal pyramidal

Question 3

What is a bonding pair and lone pair

Answer 3

bonding- pair of electrons in a bond
non-bonding/lone-

Question 4

Bonds in Linear

Answer 4

• 2 bonding and 0 non-bonding
  or
• 1 bonding and 3 non-bonding

Question 5

Bonds in v-shaped

Answer 5

• 2 bonding and 2 non-bonding

Question 6

Bonds in trigonal planar

Answer 6

• 3 bonding and 0 non-bonding

Question 7

Bonds in tetrahedral

Answer 7

• 4 bonding and 0 non bonding

Question 8

Bonds in trigonal pyramidal

Answer 8

• 3 bonding and 1 non-bonding

Question 9

What is a polar bond

Answer 9

-asymmetrical distribution of electrons
-distortion of the electron cloud
-imbalance in bond charges
-some atoms attracting electrons more strongly than others

Question 10

What is a non-polar bond

Answer 10

-Occur when the electronegativity of both atoms in a covalent bond are identical
-e- have an equal attraction to both atoms
-symmetrical distribution of electron density

Question 11

What are dispersion forces? How do they occur

Answer 11

-a temporary attractive force that results when the e- in two adjacent atoms occupy positions that make the atoms form temporary dipoles
-instantaneous and induced dipoles interaction
-temporary distortion of the e- cloud
-occurs due to freely moving electrons in covalent bonds

The temporary dipole(instantaneous) induces opposite movement of electrons (repel) and consequently an opposite dipole in another molecule (induced)
more electrons=more difference in the charges=more dispersion forces=more attraction

Question 12

What are dipole-dipole forces? how do they occur?

Answer 12

-attractive forces between the positive end of one polar molecule and the negative end of another polar molecule
more polar=stronger dipole forces=higher melting/boiling point

Question 13

What happens to mp and bp of dipole dipole bonds?

Answer 13

Increase as differences in electronegativity of molecules increases
-dipole forces become stronger
-more electrons to create higher temporary dipole
-with more dipole, dispersion increases=stronger bonds=greater forces of attraction

more electrons=higher bp due to increase in dispersion forces

Question 14

Describe hydrogen bonding

Answer 14

-most electronegative F, H, O = very polar bonds = very polar molecules of hydride
-electron density is pulled away from hydrogen atom leaving it with a larger partial positive charge
-this attracts non-bonding pairs of e- nearby atoms (lone pairs)

Question 15

What is an ion-dipole attraction?

Answer 15

Attraction between ion and polar molecules
-positive attracts negative side of polar molecule and vice versa
-ions with attached polar molecules (ligands) =complex ions
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