Forces between molecules

Question 1

What types of bonds hold atoms in molecules and in giant structures

Answer 1

Atoms in molecules and in giant structures are held together by strong covalent, ionic or metallic bonds

Question 2

How many types of intermolecular forces are there? What are the names of all the intermolecular forces?

Answer 2

There are three intermolecular forces;
1) van der Waals
2) dipole - dipole forces
3) hydrogen bonds

Question 2

If intermolecular forces are strong enough between molecules, what can be formed?

Answer 2

If intermolecular forces are strong enough, then molecules that are held closely together enough will become lipids or even solids

Question 3

What do van der Waal forces act between?
What do dipole - dipole forces act between?
What do hydrogen bonds act between?

Answer 3

van der Waals act between all atoms and molecules
dipole - dipole forces act only between certain types of molecules
hydrogen bonds act only between certain type of molecules

Question 4

What forces hold together molecules and separate atoms?

Answer 4

Molecules and separate atoms are attracted to one another by other weaker forces, called intermolecular forces

Question 5

What is the rank order of strength between van der Waals, dipole - dipole forces and hydrogen bonds?

Answer 5

1) van der Waals - weakest

2) dipole - dipole forces - medium

3) hydrogen bonds - strongest

Question 5

If a molecule has more than one polar bond, what occurs commonly? If a molecule has more than one polar bond what main also occur depending on the shape of the molecule?

Answer 5

If a molecule has more than one polar bond there may not be a dipole moment, as the effect of each bond may cancel.

If a molecule has more than one polar bond, the effects may add up and reinforce each other, but this depends on the shape of the molecule

Question 6

What type of forces act between molecules that have permanent dipoles?

Answer 6

Dipole - dipole forces act between molecules that have permanent dipoles

Question 7

When two polar molecules have dipoles, what occurs?

Answer 7

Two polar molecules that both have dipoles will attract one another. No matter their starting positions, molecules with dipoles will ‘flip’ to make an arrangement where the two molecules attract

Question 8

What are van der Waals?

Answer 8

van der Waals are a result of positive and negative charges which produce very weak electrostatic attractions between all atoms and molecules

Question 8

What types of molecules and atoms do van der Waals occur in?

Answer 8

All atoms and molecules have van der Waal forces

Question 9

How do van der Waals work?

Answer 9

The distribution of charge is constantly changing in atoms. Any arrangement within an atom will result in a temporary dipole. This dipole would then affect the electron distribution in nearby atoms as they are attracted to the atom in the particular temporary lobe

Question 10

What is a temporary dipole?

Answer 10

A temporary dipole occurs when an arrangement is formed within an atom resulting in a dipole, temporary dipoles are dipoles that happen just for an instance

Question 11

Describe what happens as the electron distribution of the original atom changes

Answer 11

As the electron distribution of the original atom changes, atoms around it will be induced to form dipoles, that will be attracted to the original atom

Question 12

What is the cause of a dipole?

Answer 12

Dipoles are caused by the changing positions of the electron cloud

Question 13

What is the name given to the forces created by the change of electron distribution of the original atom?

Answer 13

These forces created are called instantaneous dipole - induced dipole forces

Question 14

What causes the size of van der Waals to increase?

Answer 14

The size of van der Waals increases with the number of electrons present

Question 15

van der Waal sizes increase with the number of electrons, what does this mean for larger atomic or molecular masses or atom/molecules with small atomic or molecular masses?

Answer 15

Atom and molecules with larger atomic or molecular masses produce stronger van der Waals forces than atoms and molecules with small atomic or molecular masses

Question 16

What do van der Waals go to explain?

Answer 16

van der Waals explain why the boiling points of the noble gases increase as the atomic number of the noble gases increase. van der Waals also explain why the boiling points of hydrocarbons increase with increased chain length

Question 17

What is a hydrogen bond?

Answer 17

A hydrogen bond consists of a hydrogen atom sandwiched between two very electronegative atoms

Question 17

How does a hydrogen bond occur?

Answer 17

A hydrogen bond occurs when the lone pair electrons on an atom is strongly attracted to the electron deficient hydrogen atom to form a strong intermolecular force

Question 18

What are hydrogen bonds stronger than? What are hydrogen bonds also weaker than?

Answer 18

Hydrogen bonds are stronger than dipole dipole attractions, though much weaker than a covalent bond

Question 19

What two requirements are needed in order for a hydrogen bond to form

Answer 19

1) A hydrogen atom with a strong partial positive charge on the hydrogen atom

2) A very electronegative atom with lone pair of electrons to be attracted to the partially charged hydrogen atom

Question 19

What are the only atoms that are electronegative enough to form hydrogen bonds?

Answer 19

Fluorine
Nitrogen
Oxygen

Question 20

Why do the boiling points of hydrides increase?

Answer 20

The boiling points in noble gases show gradual increase in boiling points because the only forces acting between atoms are van der Waal forces which increase with the number of electrons present