Atomic structure

Question 1

What are the 3 subatomic particles?

Answer 1

Proton, neutron, electron

Question 2

What are the charges and location of protons and electrons?

Answer 2

Proton: +1, in the nucleus
Electron: -1, in orbitals around the nucleus

Question 3

What is the role of neutrons in the nucleus?

Answer 3

They add mass and help stabilise the nucleus

Question 4

What is an ion?

Answer 4

An atom or molecule with a charge due to losing or gaining electrons

Question 5

What is a cation?

Answer 5

A positively charged ion formed by losing electrons

Question 6

What is an anion?

Answer 6

A negatively charged ion formed by gaining electrons

Question 7

What is an electrolyte?

Answer 7

A substance that conducts electricity in solution by releasing ions

Question 8

What is the maximum number of electrons in an S orbital?

Answer 8

2

Question 9

What is the order of orbital filling?

Answer 9

1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f……

Question 10

What are the 4 quantum numbers?

Answer 10

n (shell)
I (subshell)
m (orbital orientation)
s (spin)

Question 11

Name the state symbols

Answer 11

aq (Aqueous)
s (Solid)
g (Gas)
l (Liquid)

Question 12

What is the formula for concentration in mol/dm³?

Answer 12

C = n/V

Question 13

What is the formula for moles using mass?

Answer 13

n = m/Mr

Question 14

How many particles are in one mole? (Avogadro’s number)

Answer 14

6.022 × 10²³

Question 15

What is the molar volume of gas at room temp?

Answer 15

24 dm³/mol (at 20°C and 1 atm)

Question 16

What is the formula to convert g/dm³ to mol/dm³?

Answer 16

C = m/(Mr x V)

Question 17

What is ionisation energy?

Answer 17

The energy needed to remove one mole of electrons from one mole of gaseous atoms

Question 18

Why is the second ionisation energy higher than the first?

Answer 18

Because it’s harder to remove an electron from a positively charged ion

Question 19

What factors affect ionisation energy?

Answer 19

Atomic radius, nuclear charge, shielding, orbital stability

Question 20

How does atomic radius affect ionisation energy?

Answer 20

Larger atoms = lower ionisation energy (electrons are further away)

Question 21

How does nuclear charge affect ionisation energy?

Answer 21

More protons = higher attraction = higher ionisation energy

Question 22

How does shielding affect ionisation energy?

Answer 22

More inner shells = more shielding = lower ionisation energy

Question 23

Why is it easier to remove paired electrons?

Answer 23

They repel each other slightly

Question 24

What is relative atomic mass (Ar)?

Answer 24

The average mass of isotopes compared to 1/12 of carbon-12

Question 25

What is the relative molecular mass (Mr)?

Answer 25

The sum of Ar values in a molecule

Question 26

What is radioactivity?

Answer 26

Spontaneous emission of radiation from an unstable nucleus

Question 27

What are the three types of radiation?

Answer 27

Alpha, Beta, Gamma

Question 28

What is alpha radiation?

Answer 28

2 protons + 2 neutrons (He nucleus) (low penetration)

Question 29

What is beta radiation?

Answer 29

High-speed electron from nucleus. (medium penetration)

Question 30

What is gamma radiation?

Answer 30

High-energy wave, no mass or charge. (high penetration)

Question 31

What is a radioactive isotope?

Answer 31

An unstable isotope that emits radiation to become stable

Question 32

What is a half life?

Answer 32

The time required for a substance to reduce to half of its initial value

Question 33

How do you calculate decay?

Answer 33

N = N₀ × (½)ⁿ, where n = number of half-lives

Question 34

What is radioactivity?

Answer 34

Radioactivity is the spontaneous emission of particles or electromagnetic radiation from an unstable atomic nucleus.

Question 35

What factors influence the stability of an atomic nucleus?

Answer 35

The neutron/proton (n/p) ratio, total nuclear charge, and whether the nucleus is light or heavy.

Question 36

How does the n/p ratio affect nuclear stability?

Answer 36

Light nuclei are more stable with n/p ≈ 1. Heavy nuclei require higher n/p ratios for stability. An odd n/p ratio often leads to instability.

Question 37

What are the main types of radioactive decay and their associated radiations?

Answer 37

Alpha decay (α): emission of helium nucleus; Beta decay (β): neutron/proton conversion; Gamma radiation (γ): emission of high-energy photons; Positron emission (β⁺): for light nuclei with n/p < 1; Electron capture (EC): proton turns into neutron by capturing orbital electron.

Question 38

What occurs during electron capture?

Answer 38

An inner-shell electron is captured by the nucleus, converting a proton into a neutron and emitting a neutrino (νₑ) and an X-ray.

Question 39

What are the modern and old units for measuring radiation activity?

Answer 39

New: Becquerel (Bq) = 1 disintegration/sec. Old: Curie (Ci) = 3.7 × 10¹⁰ disintegrations/sec.

Question 40

What are the modern and old units for absorbed radiation dose?

Answer 40

New: Gray (Gy) = 1 J/kg. Old: rad. 1 rad = 0.01 Gy.

Question 41

What are the modern and old units for biological damage from radiation?

Answer 41

New: Sievert (Sv). Old: rem. 1 rem = 0.01 Sv.

Question 42

What are the radiation weighting factors used in Sievert calculations?

Answer 42

1 for β, γ, and X-rays; 10 for high-energy protons and neutrons; 20 for α-radiation.

Question 43

What is the general form of the radioactive decay equation?

Answer 43

ln[N] = ln[N₀] - λt. ## Footnote Example: ln[¹³¹I] = 2.9957 - 0.0866·t

Question 44

What is half-life?

Answer 44

The time it takes for half of the radioactive nuclei in a sample to decay.

Question 45

How are natural radioisotopes formed?

Answer 45

They originate from long-lived isotopes and can be produced by cosmic ray interactions.

Question 46

How are artificial radioisotopes produced?

Answer 46

By transmutation: bombarding stable isotopes with α-particles, protons, or neutrons.

Question 47

What are some applications of radioactive isotopes?

Answer 47

Carbon dating, radioimmunoassay, medical imaging and treatment, nuclear energy generation.

Question 48

What’s the difference between nuclear fission and fusion?

Answer 48

Fission splits heavy nuclei to release energy. Fusion combines light nuclei to form a heavier nucleus, releasing energy.

Question 49

Why are heavy nuclei typically unstable?

Answer 49

Heavy nuclei have many protons, which create strong electrostatic repulsion. ## Footnote More neutrons are needed to add nuclear binding through the strong force.

Question 50

What happens if the neutron-to-proton (n/p) ratio isn't high enough?

Answer 50

The nucleus becomes unstable and undergoes radioactive decay.