Atomic Structure & Mass

Question 1

What are the three subatomic particles that make up an atom?

Answer 1

Protons, neutrons, and electrons.

Question 2

What is the charge and relative mass of a proton?

Answer 2

Charge: +1, Relative mass: ~1 atomic mass unit (amu).

Question 3

What is the charge and relative mass of a neutron?

Answer 3

Charge: 0 (neutral), Relative mass: ~1 amu.

Question 4

What is the charge and relative mass of an electron?

Answer 4

Charge: -1, Relative mass: ~1/1836 amu.

Question 5

Where are protons and neutrons located in an atom?

Answer 5

In the nucleus.

Question 6

Where are electrons located in an atom?

Answer 6

In orbitals around the nucleus.

Question 7

What determines the atomic number of an element?

Answer 7

The number of protons in the nucleus.

Question 8

What is the mass number (nucleon number) of an atom?

Answer 8

The sum of protons and neutrons in the nucleus.

Question 9

What is an isotope?

Answer 9

Atoms of the same element with the same number of protons but different numbers of neutrons.

Question 10

How do isotopes of the same element differ in properties?

Answer 10

They have the same chemical properties but different physical properties, such as mass and stability.

Question 11

How is an element’s atomic symbol written?

Answer 11

Example: [ \, ^{A}_{Z}X ] where A = mass number, Z = atomic number, X = element symbol.

Question 12

What does the atomic number represent?

Answer 12

The number of protons (and electrons in a neutral atom).

Question 13

What does the mass number represent?

Answer 13

The total number of protons and neutrons in the nucleus.

Question 14

What are stable isotopes?

Answer 14

Isotopes that do not undergo radioactive decay over time.

Question 15

What are unstable isotopes?

Answer 15

Isotopes that decay over time, emitting radiation.

Question 16

What is an energy level in an atom?

Answer 16

A discrete region where electrons exist at fixed distances from the nucleus.

Question 17

What is the maximum number of electrons in the first four energy levels?

Answer 17

1st: 2, 2nd: 8, 3rd: 18, 4th: 32.

Question 18

What is the Aufbau principle?

Answer 18

Electrons fill the lowest available energy levels first.

Question 19

What is Hund’s rule?

Answer 19

Electrons occupy orbitals singly before pairing up.

Question 20

What is the Pauli exclusion principle?

Answer 20

No two electrons in an atom can have the same set of four quantum numbers.

Question 21

What are the four types of orbitals?

Answer 21

s, p, d, f.

Question 22

How many electrons can each type of orbital hold?

Answer 22

s: 2, p: 6, d: 10, f: 14.

Question 23

What is the electron configuration of oxygen (Z = 8)?

Answer 23

1s² 2s² 2p⁴.

Question 24

How does electron configuration determine an element’s chemical properties?

Answer 24

Valence electrons determine reactivity and bonding behavior.

Question 25

How is relative atomic mass (Ar) calculated?

Answer 25

Weighted average of isotope masses: \[ Ar = \frac{(mass \times abundance) + (mass \times abundance)}{100} \]

Question 26

Why isn’t the relative atomic mass always a whole number?

Answer 26

It accounts for the weighted average of all isotopes of the element.

Question 27

What is the relative atomic mass of chlorine if Cl-35 (75%) and Cl-37 (25%) exist?

Answer 27

\[ Ar = \frac{(35 \times 75) + (37 \times 25)}{100} = 35.5 \]

Question 28

What is a flame test used for?

Answer 28

Identifying metal ions based on the color they emit in a flame.

Question 29

What color does sodium produce in a flame test?

Answer 29

Yellow.

Question 30

What color does copper produce in a flame test?

Answer 30

Blue-green.

Question 31

How does the Bohr model explain atomic spectra?

Answer 31

Electrons absorb energy and jump to higher levels, then emit light as they fall back.

Question 32

How does the Schrödinger model differ from the Bohr model?

Answer 32

It describes electron orbitals as probability clouds rather than fixed orbits.

Question 33

What are the three main types of radioactive decay?

Answer 33

Alpha (α), Beta (β), Gamma (γ).

Question 34

What is an alpha particle?

Answer 34

A helium nucleus (2 protons, 2 neutrons).

Question 35

What is a beta particle?

Answer 35

A high-speed electron or positron.

Question 36

What is gamma radiation?

Answer 36

High-energy electromagnetic waves.

Question 37

What is a nuclear equation for alpha decay?

Answer 37

\[ ^{238}_{92}U \rightarrow ^{234}_{90}Th + ^{4}_{2}He \]

Question 38

What is a nuclear equation for beta decay?

Answer 38

\[ ^{14}_{6}C \rightarrow ^{14}_{7}N + e^- \]

Question 39

What is half-life?

Answer 39

The time required for half of a radioactive substance to decay.

Question 40

Give an example of a human-made radioisotope.

Answer 40

Technetium-99m, used in medical imaging.

Question 41

What is carbon-14 dating?

Answer 41

A method for determining the age of organic materials using the decay of carbon-14.

Question 42

What is nuclear fission?

Answer 42

Splitting of a heavy nucleus into lighter nuclei, releasing energy.

Question 43

What is nuclear fusion?

Answer 43

The combining of light nuclei into a heavier nucleus, releasing massive energy.