VESPR theory

Question 1

What does VESPR theory stand for?

Answer 1

Valence shell electron pair repulsion theory

Question 2

What does VESPR help scientists do?

Answer 2

predict a 3d shape of a molecule centered around a central atom

Question 3

Why do molecules form geometric shapes?

Answer 3

Electrons don’t want to be next to each other because like repels like and the negative charges repel each other. Since there are several electron, the electrons have to find positions where they are as far away from each other as possible

Question 4

What are the two main rules in VESPR theory?

Answer 4

Electron pairs in the valence shell of an atom will repel or move away from each other
nonbonded electron pairs are found closer to the atom and exhibit more repulsion than nonbonded pairs

Question 5

What are the 5 basic shapes of VESPR molecules?

Answer 5

in this def, a “line” can be a single, double, or triple bond
-linear (1 or 2 “lines”, just a straight line)
-trigonal planar (one atom in the middle and 3 “lines, looks like half of a pyramid)
-tetrahedral (one atom in the middle and 4 “lines”, looks like a pyramid. all faces of the shape created are triangles)
-trigonal bipyramidal (2 pyramids that share a base, 1 central atom and 5 “lines”)
octahedral (vertices make up an octahedron when connected, 1 central atom and 6 “lines”)

Question 6

How can you figure out the angles within the VESPR structures?

Answer 6

Since electrons want to get as far away from each other as possible, their angles are 360/the number of “lines”
(in our def, a “line” is any kind of bond - single, double, etc)

Question 7

Covalent bonds can be ____ or ______

Answer 7

polar or nonpolar

Question 8

Why is polarity important?

Answer 8

It determines other physical properties of the compound, like boiling point, melting point, solubility, and intermolecular interactions

Question 9

What are nonpolar bonds?

Answer 9

Bonds where the atoms share electrons equally because of similar electronegativities
(in other words, compounds with elements with similar electronegativities will be nonpolar)

Question 10

What are polar bonds?

Answer 10

Bonds where the atoms share the electrons unequally because the atom have different electronegativities

Question 11

All ionic bonds are ____

Answer 11

polar

Question 12

What is a dipole?

Answer 12

The small difference in charge that occurs when one atom is closer to the bonded electron pair

Question 13

What does δ+ mean (in reference to dipoles)

Answer 13

slightly positive

Question 14

What does δ- mean (in reference to dipoles)

Answer 14

slightly negative

Question 15

What is a dipole moment? How is it shown?

Answer 15

the occurrence of a dipole
an arrow that shows which direction the electrons are moving to (the element accepting the electron). There is also a small vertical line that shows which element is donating the electron)
(look up “dipole moment” for references)

Question 16

Nonpolar covalent bonds form between atoms with an electronegativity difference between _ and ___

Answer 16

0

0. 4
   (ex: carbon and hydrogen have respective electronegativities of 2.5 and 2.1, which have a difference of 0.4. their compound is nonpolar)

Question 17

Polar covalent bonds form between atoms with an electronegativity difference between __ and __

Answer 17

0. 5

1. 7

Question 18

Bonds are polar if ______. The entire molecule is polar if _____

Answer 18

the atoms have an electronegativity difference greater than 0.5
the shape is asymmetric (SNAP: Symmetrical molecules are Nonpolar and Asymmetric molecules are Polar)

Question 19

Can a molecule be nonpolar but the bonds are polar at the same time?

Answer 19

Yes

Question 20

What does it mean if bonding atoms are delocalized?

Answer 20

They are free to move around

Question 21

How do metallic bonds form?

Answer 21

Bonding atoms are delocalized and form a negative electron sea around positive cations.

Question 22

What are some properties of metals with metallic bonds?

Answer 22

• good conductor of electricity and heat
• high melting point and high boiling point
• high density
• malleable and ductile

Question 23

What does the strength of a metallic bond depend on?

Answer 23

The number of electrons free to move around the metal and the size and charge of the cation.

Question 24

What is an intramolecular force?

Answer 24

A force that holds the molecule together

Question 25

What is an intermolecular force?

Answer 25

The forces between molecules that influence their physical properties

Question 26

List the intermolecular forces from weakest to strongest

Answer 26

London dispersion force
Dipole-Dipole interactions
Hydrogen bonding

Question 27

What are London dispersion forces?

Answer 27

weak attractive forces that are created by the movement of electron which attracts the positive nucleus of another atom
-leads to a temporary dipole that loosely keeps atoms together

Question 28

How do london dispersion forces get stronger?

Answer 28

With more electrons

Question 29

What are dipole forces?

Answer 29

Attraction forces between two polar molecules (opposite charges attract, positive end of polar molecule attracts negative end of other polar molecule)

Question 30

The larger the dipole moment, the larger the _____ in dipole dipole interactions

Answer 30

attractive force

Question 31

What is a dipole moment?

Answer 31

Measurement of the size of a dipole

Question 32

Are hydrogen bonds actual bonds?

Answer 32

NO

much weaker than covalent, metallic, or ionic bonding

Question 33

Hydrogen bonds are the intermolecular forces between which elements?

Answer 33

Hydrogen, Fluorine, Oxygen, and Nitrogen

Question 34

How do intermolecular force relate to the different states of matter?

Answer 34

Solids have strong intermolecular forces
liquids have medium strength intermolecular forces
gases have weak intermolecular forces

Question 35

What does having weaker intermolecular forces mean?

Answer 35

Lower boiling points and melting points

Question 36

What does having stronger intermolecular forces mean?

Answer 36

Higher boiling points and melting points

Question 37

What intermolecular forces can Noble gases have?

Answer 37

Only London dispersion forces