20.1-Radioactivity

Nuclear Chemistry:

Radioactive Decay and Nuclear Bombardment Reactions:

Antoine Henri Becquerel discovered in 1896 that photographic plates developed bright spots when exposed to uranium minerals and concluded that they must give off radiation.

Terms:

α = alpha particle = positively charged, consist of helium-4 nuclei (nuclei with two protons and two neutrons)
β = beta particle = negatively charged, consist of high speed electrons
γ = gamma particle = no charge = a form of electromagnetic radiation similar to x-rays except higher in energy.

Nuclide Symbol: ^A_ZX
Example: ²³⁸₉₂U → Uranium–238
X = element
Z = atomic number → number of protons → p⁺
A = mass number → number of protons and neutrons → n^o
number of neutrons = N = A – Z

A gives the mass of the isotope
Z gives the charge

isotopes → same Z, same element. Ex: ¹²₆C, ¹³₆C, ¹⁴₆C
nuclides → technically any combination ¹²₆C, ¹⁴₇N, ¹⁸₈O

*But now these terms are used interchangeably

Notation:

protons → ¹₁H, ¹₁p, p⁺
neutrons → ¹₀n, n^o, n
electrons → ⁰_{– 1}e, ⁰_{– 1}β (high energy beta particle), β^–
positron → ⁰₁e, ⁰_{+ 1}β (like a positive electron), β⁺
gamma photon → ⁰₀γ, γ
alpha particle → ⁴₂He, α
deuterium → ²₁H, D, d (H plus one neutron)
tritium → ³₁H, t (H plus two neutrons)

Radioactive Decay: has one reactant, occurs naturally, no energy input needed. Usually, high energy particles come out.

Example:

Nuclear Equation:
²³⁸₉₂U → ²³⁴₉₀Th + ⁴₂He

These must be mass balanced and charge balanced (superscripts and subscripts on the left side of the equation equal the sum of the superscripts and subscripts on the right side of the equation.)

Nuclear Bombardment Reactions: has two reactants. Usually synthesized and energy input is required.

Example:

^□_□□ + ²₁H → ²⁴₁₁Na + ⁴₂He

^□_□□ = ²⁶₁₂Mg