Lecture 1: Introduction & Chemical Bonds

Question 1

What is the nucleus made up of?

Answer 1

Protons and Neutrons

Question 2

How many protons does an atom with 6 electrons have?

Answer 2

6 protons(atoms have the same number of protons and electrons)

Question 3

What is the atomic number?

Answer 3

The number of protons in a specific elements atom(this is how elements identify)

Question 4

What is the mass number?

Answer 4

The number of protons plus the number of neutrons

Question 5

Atomic Mass vs Mass Number

Answer 5

Mass Number: Number of protons and neutrons in an atom
Atomic Mass: The average number of protons and neutrons for all natural isotopes of an element.

Question 6

What is the atomic mass?

Answer 6

The average number of protons and neutrons for all natural isotopes of an element.

Question 7

What is an isotope?

Answer 7

Two atoms of the same element that have the same number of protons but differ in neutrons.

Question 8

Isotopes with neutrons

Answer 8

Are more unstable(radioactive) and due to that are important in biology and medicine

Question 9

Rows in the periodic table

Answer 9

Elements all have their electrons in the same shell and are all similar sizes

Question 10

Columns in the periodic table

Answer 10

Elements have the same number of valence electrons and have similar chemical properties

Question 11

Covalent Bonds

Answer 11

• Molecules
• Two atoms share electrons

Question 12

Non-polar Covalent Bond

Answer 12

Electrons are equally distributed between the two atoms

Question 13

Polar Covalent Bond

Answer 13

Electrons are unequally distributed between two atoms(due to difference in electronegativity)

Question 14

Hydrogen Bond

Answer 14

Polar covalent bond between hydrogen and N, O or F (caused by large difference in electronegativity)

Question 15

Which is stronger the covalent bond or the hydrogen bond?

Answer 15

Covalent bond

Question 16

Water molecules and hydrogen bonding

Answer 16

Hydrogen bonds form between H2O molecules. This creates a network of hydrogen bonds which has a large overall strength

Question 17

Why can spiders walk on water?

Answer 17

Spiders can walk on water because of the network of hydrogen bonds that is strong enough to support small animals(surface tension)

Question 18

Four phenomena that result from hydrogen bonding between water molecules

Answer 18

1. Surface tension
2. Meniscus
3. Ice
4. Chemical Reactions

Question 19

Why does a meniscus form when water is poured into a glass?

Answer 19

Water molecules at the surface experience a downward pull from water molecules below, to counteract this the water molecules will adhere to the sides of the glass to resist the downward pull

Question 20

How does water travel up tree trunks?

Answer 20

Evaporation occurs at the top of the tree pulling all of the water molecules up the tree since they are all bonded together

Question 21

Is ice more dense than liquid water?

Answer 21

No, liquid water is more dense than frozen water

Question 22

Two most common elements in biology?

Answer 22

1. Hydrogen
2. Carbon

Question 23

Unit for atomic mass and why is can’t be gram?

Answer 23

Unit: Daltons(D)
Can’t be grams because the number would be EXTREMELY small

Question 24

What determines the shape of a molecule?

Answer 24

The shape of the orbitals

Question 25

What is electronegativity?

Answer 25

Measure of how strongly electrons are attracted to the nucleus

Question 26

What elements are more electronegative?

Answer 26

Elements with more protons are more electronegative

Question 27

Why do electrons determine the ability of atoms to combine with other atoms?

Answer 27

Only electrons are involved in bonds. Hence the distribution and the amount of electrons available for interaction is critical for atoms to combine with other atoms.