Week 2: Atomic Number and Atomic Mass

Question 1

What is Atomic Mass?

Answer 1

Protons + Neutrons

Question 2

What is Atomic Number?

Answer 2

Number of protons (same as electrons unless an ion)

Question 3

What are isoptopes?

Answer 3

Same element with a different number of neutrons and therefore different atomic mass.

Question 4

Why can the periodic table show an element with a decimal as it’s atomic mass?

Answer 4

An average is taken of all possible isotopes present on Earth.

Question 5

What is the equation for relative isotopic mass?

Answer 5

Σ (Isotopic Mass x Abundance (%) ) / 100 (Total Abundance)

Question 6

Which atoms are stable?

Answer 6

Atoms with a full outer shell.

Question 7

What does the chemical properties of substances elements rely on?

Answer 7

How many electrons are present in their outer shell.

Question 8

Which groups are metals?

Answer 8

Group 1 and 2

Question 9

What are cations?

Answer 9

Ions with a positive charge (Group 1 and 2 ions)

Question 10

Which groups are non-metals?

Answer 10

Group 6 and 7

Question 11

What are anions?

Answer 11

Ions with a negative charge

Question 12

What was Bohr’s Atomic Model?

Answer 12

The first model proposing that electrons were not found at random in the atom but at certain distances from the nucleus, arranged in shells.

Features of his model include:
- Each shell of electrons is at a definite radius from the nucleus.
- The electrons in each shell have equal energy.
- Shells further from the nucleus are higher energy than those closer.
- Electrons occupy the lowest energy shell possible.

Question 13

What are nucleons?

Answer 13

The particles which make up the nucleus.

Question 14

Which two particles are the nucleons?

Answer 14

Proton and Neutron

Question 15

What is the relative mass and relative charge of a proton?

Answer 15

RM = 1
RC = +1

Question 16

What is the relative mass and relative charge of a neutron?

Answer 16

RM = 1
RC = 0

Question 17

What is the relative mass and relative charge of an electron?

Answer 17

RM = Negligible (1/1840)
RC = -1

Question 18

What are sublevels Why are they important?

Answer 18

• Within the shells/energy levels of the Bohr model, there are sublevels.
• Here, electrons have small but significant differences in energy.
• They help to explain the chemistry of many elements and compounds.

Question 19

What are the four sublevels?

Answer 19

s, p, d, f

Question 20

How many electrons does the s sublevel contain?

Answer 20

2

Question 21

How many electrons does the p sublevel contain

Answer 21

6

Question 22

How many electrons does the d sublevel contain?

Answer 22

10

Question 23

How many electrons does the f sublevel contain?

Answer 23

14

Question 24

What are orbitals?

Answer 24

• Electrons exist as orbitals.
• These are volumes where the electron is likely to be found as they are too small to pin down very accurately and have the characteristics of a wave which makes their exact position hard to pin know.

(Different to Bohr’s model which has electrons at a certain radii)

Question 25

How many electrons can an orbital hold?

Answer 25

2

(Therefore s = 1 orbital, p = 3 orbitals etc.)

Question 26

Do orbitals have identical energy levels?

Answer 26

• If they are in the same sublevel, yes.
• s < p < d < f

Question 27

What is Hund’s rule?

Answer 27

Electrons go into the p orbitals separately rather than pairing up in a single orbital.