Unit 1 - Structure and Bonding

Question 1

What is a covalent bond, and how is it held together?

Answer 1

A shared pair of electrons between two positively charged nuclei, held together by their common attraction for the shared electrons.

Question 2

When are polar covalent bonds formed?

Answer 2

When the electronegativities of the atoms bonding is different, but not different enough to be ionic.

Question 3

What can be used to indicate the partial charges on atoms?

Answer 3

Delta positive (δ+) and delta negative (δ-) notation (this gives a rise to dipoles)

Question 4

When are pure covalent bonds formed?

Answer 4

When the electronegativities of atoms bonding are identical.

Question 5

What is an ionic bond?

Answer 5

The electrostatic force of attraction between positive and negative ions.

Question 6

How is an ionic compound structured?

Answer 6

They form lattice structure of oppositely charged ions.

Question 7

What is the positioning of pure covalent, ionic, and polar covalent bonding on a bonding continuum?

Answer 7

Pure covalent bonding and ionic bonding can be considered as opposite end of bonding continuum, with polar covalent lying between those two extremes.

https://prnt.sc/gnsfaXN9QMbk

Question 8

What gives an indication of the ionic character?

Answer 8

The difference in electronegativity between bonded atoms.

Question 9

The larger the difference in electronegativity…

Answer 9

The more polar the bond will be.

Question 10

If the difference in electronegativities is large, what happens to the movement of bonding electrons?

Answer 10

The movement of bonding electrons from the element of lower electronegativity to the element of higher electronegativity is complete, resulting in the formation of ions.

Question 11

When are compounds often ionic?

Answer 11

When bond is formed between metals and non-metals.

Question 12

What are van der waal forces?

Answer 12

intermolecular forces acting between molecules

Question 13

What are the three different van der waal forces?

Answer 13

London dispersion forces,
permanent dipole - permanent dipole interactions
hydrogen bonding

Question 14

What are london dispersion forces?

Answer 14

Forces of attraction that can operate between all atoms and molecules
These forces are much weaker than all other types of bonding.

Question 15

How are LDFs formed?

Answer 15

As a result of electrostatic attraction between temporary dipoles and induced dipoles caused by movement of electrons in atoms and molecules.

Question 16

What is the strength of LDFs related to?

Answer 16

The number of electrons within an atom or molecule.

Question 17

When is a molecule described as polar?

Answer 17

If it has a permanent dipole.

Question 18

What are pd-pd interactions?

Answer 18

Additional electrostatic forces of attraction between polar molecules.

Question 19

Are pd-pd interactions or LDFs stronger?

Answer 19

pd-pd interactions are stronger than LDFs for molecules with similar numbers of electrons.

Question 20

What element will typically suggest a bond is highly polar?

Answer 20

Bonds consisting of hydrogen atoms bonded to an atom of a strong electronegative element such as flourine, oxygen, or nitrogen

Question 21

What are hydrogen bonds?

Answer 21

A permanent dipole to permanent dipole attraction that occurs when a hydrogen atom os covalently bonded to a highly electronegative element, e.g. flourine, nitrogen, oxygen.

Question 22

What is the soubility of non-polar molecular substances?

Answer 22

Tend to be solube in non-polar solvents and insoluble in polar solvents.

Question 23

How strong are hydrogen bonds?

Answer 23

Stronger than other forms of pd-pd interactions, but weaker than a covalent bond.

Question 24

What features must be considered to predict solubility of a compound?

Answer 24

• Presence of O-H or N-H bonds, which implies hydrogen bonding.
• Spatial arrangemants of polar covalent bonds, resulting in a molecule possessing a permanent dipole.

Question 25

What can we observe an anomoly in boiling point under due to hydrogen bonding?

Answer 25

Ammonia, water, and hydrogen flouride.

Question 26

What is the solubility of ionic compounds and polar molecular compounds?

Answer 26

They tend to be solube in polar solvents like water, and insoluble in non-polar solvents.

Question 27

Boiling points, melting points, viscosity and solubility/miscibility in water are properties of…

Answer 27

Substances that are affected by hydrogen bonding.

Question 28

What are the melting point and boiling points of polar vs non polar substances?

Answer 28

mp and bp of polar substances is higher than the mp and bp of non-polar substances with similar electrons.