Chemical Changes & Structure

Question 1

What is a pure/non-polar covalent bond?

Answer 1

A bond which exists when two atoms share the electrons within the bond equally

Question 2

What is a polar covalent bond?

Answer 2

When the atoms involved in a covalent bond share the electrons unequally

Question 3

When are ionic bonds formed?

Answer 3

In atoms with a large difference in electronegativity, usually between metal atoms bonded to non-metal atoms

Question 4

What are the three types of van der Waals’/Intermolecular forces?

Answer 4

-Hydrogen Bonding
-Permanent Dipole- Permanent Dipole Interactions
-London Dispersion Forces

Question 5

What results in LDFs?

Answer 5

An uneven distribution of constantly moving electrons around each nuclei of an atom. As the electrons are constantly moving they form temporary dipoles which induce other temporary dipoles in atoms nearby. When these attract each other, they form London Dispersion Forces

Question 6

How are permanent dipole to permanent dipole interactions formed?

Answer 6

When a polar covalent bond is formed between two atoms with an electronegativity difference 0.5 or greater. This permanent dipole is attracted to other permanent dipoles in other molecules.

Question 7

What are permanent dipole to permanent dipole interactions?

Answer 7

Electrostatic attractions between permanently positive and negative areas of polar molecules

Question 8

Why do molecules containing PD-PD interactions have higher melting and Boiling Points than molecules of a similar size?

Answer 8

PD-PD interactions are stronger than LDFs

Question 9

How does hydrogen bonding arise?

Answer 9

When hydrogen is bonded to the more electronegative atoms of Nitrogen, Oxygen and Fluorine

Question 10

Why does ice float on water?

Answer 10

Waters solid form is less dense than its liquid form.
This is because in ice hydrogen bonds lock the water molecules into a lattice of hexagonal rings leaving lots of empty space between the molecules.