Atomic Structure & Nuclear Stability

Constituents of the atom, specific charge, isotopes, the strong nuclear force, and alpha/beta decay equations.

Spec Points Covered
  • State the constituents of an atom and their properties (chargeA property of matter that causes it to experience a force in an electromagnetic field. Measured in coulombs (C)., mass).
  • Calculate the specific chargeA property of matter that causes it to experience a force in an electromagnetic field. Measured in coulombs (C). of nuclei, ions and subatomic particles.
  • Use AZX notation and determine nucleon number, proton number and neutron number.
  • Define isotopes and interpret isotopic data.
  • Describe how the strong nuclear force varies with nucleon separation.
  • Compare the strong nuclear force and the electrostatic repulsion between protons.
  • Write balanced decay equations for alpha, beta-minus and beta-plus decay.
  • Explain the role of neutrinos and anti-neutrinos in beta decay.
Notes
01 Atoms are made of protons, neutrons and electrons 3.2.1.1 → 02 Specific charge is the ratio of charge to mass Specific charge 3.2.1.1 → 03 AZX notation describes any nucleus 3.2.1.1 → 04 Isotopes have the same proton number but different nucleon numbers Isotopes 3.2.1.1 → 05 The strong nuclear force holds the nucleus together Strong nuclear force 3.2.1.2 → 06 Alpha decay ejects a helium nucleus ${}_{Z}^{A}X \longrightarrow {}_{Z-2}^{A-4}Y + {}_{2}^{4}\alpha$ 3.2.1.2 → 07 Beta-minus decay converts a neutron into a proton ${}_{Z}^{A}X \longrightarrow {}_{Z+1}^{A}Y + {}_{-1}^{0}\beta + {}_{0}^{0}\bar{\nu}_{e}$ 3.2.1.2 → 08 Beta-plus decay converts a proton into a neutron ${}_{Z}^{A}X \longrightarrow {}_{Z-1}^{A}Y + {}_{+1}^{0}\beta + {}_{0}^{0}\nu_{e}$ 3.2.1.2 → 09 Neutrinos were hypothesised to conserve energy in beta decay 3.2.1.2 →
Σ Key Equations Full Reference →
On Data Sheet
Not on Data Sheet
Specific charge
$$\text{specific charge} = \frac{Q}{m}$$
  • Where:
    • $Q$ = total charge (C)
    • $m$ = total mass (kg)
Used for particles, ions and nuclei. For ions, Q depends on electrons gained/lost. For nuclei, Q = Ze.
Alpha decay
$${}_{Z}^{A}X \longrightarrow {}_{Z-2}^{A-4}Y + {}_{2}^{4}\alpha$$
  • Where:
    • $A$ = nucleon number
    • $Z$ = proton number
    • $X$ = parent nucleus
    • $Y$ = daughter nucleus
Alpha particle = helium-4 nucleus. Nucleon number drops by 4, proton number drops by 2.
Beta-minus decay
$${}_{Z}^{A}X \longrightarrow {}_{Z+1}^{A}Y + {}_{-1}^{0}\beta + {}_{0}^{0}\bar{\nu}_{e}$$
  • Where:
    • $A$ = nucleon number (unchanged)
    • $Z$ = proton number (increases by 1)
Neutron → proton + electron + anti-electron neutrino.
Beta-plus decay
$${}_{Z}^{A}X \longrightarrow {}_{Z-1}^{A}Y + {}_{+1}^{0}\beta + {}_{0}^{0}\nu_{e}$$
  • Where:
    • $A$ = nucleon number (unchanged)
    • $Z$ = proton number (decreases by 1)
Proton → neutron + positron + electron neutrino.
Q Retrieval Practice All 12 Questions →
Q1. State the three particles that make up an atom and give their charges.
  • Proton (chargeA property of matter that causes it to experience a force in an electromagnetic field. Measured in coulombs (C). +1.60 × 10⁻¹⁹ C), neutron (charge 0), electron (charge −1.60 × 10⁻¹⁹ C).
  • Protons and neutrons are in the nucleus; electrons orbit the nucleus.
Q2. Define specific charge and state its units.
  • The ratio of the total charge of a particle to its mass.
  • Units: C kg⁻¹.
Q3. State the specific charge of an electron and a proton.
  • Electron: 1.76 × 10¹¹ C kg⁻¹.
  • Proton: 9.58 × 10⁷ C kg⁻¹.
  • Both are on the data sheet.
Q4. What do A and Z represent in ᴬ_Z X notation?
  • A = nucleon number (total protons + neutrons).
  • Z = proton number (total protons).
  • Number of neutrons = A − Z.
Q5. Define isotopes.
Nuclei that have the same number of protons but different numbers of neutrons.