Potassium Argon Dating: Formula, Working, & Limitations

Ans. Radioactivity is the process of the nuclear phenomenon in which decay of the unstable nucleus takes place. It has two forces, one is the attraction forces of the nucleus and another is the force of repulsion, which helps the nucleus be together. There are three types of nuclear decay, they are:

1. Alpha (α) decay: Helium is emitted.
2. Beta (β) decay: Electrons are emitted.
3. Gamma (γ) decay: High energy of protons are emitted.

Ans. The Potassium Argon Dating method or process is used to measure the time of origin of rocks by the ratio of radioactive argon to radioactive potassium in the rocks. This method is used in finding the age samples. The potassium argon dating (K-Ar) method is based on the relative amounts of atoms of radioactive. The method is based on rocks of decay of radioactive potassium-40 to radioactive argon-40. This potassium-40 decays to calcium-40.

The most important factor on which potassium-argon dating is dependent is radioactivity. Through the transformation of elements like radioactive potassium into radioactive argon, the age of the sample can be observed. The ratio between radioactive potassium, argon, and calcium is measured. Comparison is made with radioactivity time. 

Ans. Potassium-argon dating has the basic advantage that argon is an inert gas so it does not react chemically and is not expected to be included in the solidification of rock. Since the argon escapes from the rock, it melts. As potassium occurs as 3 isotopes. The radioactive potassium-40 decays to two by beta decay to 40Ca and by electron capture to 40Ar. Potassium is consistent with many common minerals and comes with a tiny fraction of radioactive K-40.

Ans. Radioactive decay is the method caused due to radiation of emitting energy from an unstable atomic nucleus. There are three most common types of radioactivity decay. They are alpha decay (α-decay), beta decay (β-decay), and gamma decay (γ-decay). The alpha and gamma are governed by electromagnetic forces whereas, beta decay is governed by weak forces. Alpha decay is a method, where a nucleus emits an alpha particle (helium nucleus). Alpha decay formula is given below:

E = (m_i − m_f − m_p) c²

Where,

m_i = initial mass of the nucleus

m_f = mass of the nucleus after alpha particle emission

m_p = mass of the emitted alpha particle

Beta decay is a method, where a beta particle is emitted from an atomic nucleus. Following is an example of it:

²³⁴Th₉₀ → ²³⁴Pa₉₁ + ⁰e_-1

When the nucleus' high energy level transforms to a lower energy level, the emission of photons has MeV energy, it is called gamma-ray.

Ans. The nuclear force is used in different fields. Following are included examples:

• In nuclear power plants, nuclear force generates energy, like electricity.
• Radiocarbon Dating nuclear forces are used for origin 
• The fusion process of Hydrogen into Helium in the Sun.
• Holding the nucleus together forces of nuclear play an important role
• Nuclear weapons cause huge destruction to the areas because they release a huge amount of energy.

Ans. 1u = 1.6605 × 10^–27 kg

To convert it into energy units, we multiply it by c² and find that

energy equivalent = 1.6605 × 10²⁷ × (2.9979 × 10⁸)² kg m²/s²

= 1.4924 × 10¹⁰ J

= 1.4924 × 10¹⁰ / 1.602 × 10¹⁹  eV

= 0.9315 × 10⁹ eV

= 931.5 MeV

or, 1u = 931.5 MeV/c²

For ¹⁶O₈,  ∆M = 0.13691 u = 0.13691 × 931.5 MeV/c²

= 127.5 MeV/c²

The energy needed to separate ¹⁶O₈ into its constituents is thus 127.5 MeV/c².

Ans. Isotopes are chemical variants of particular elements which have the same atomic number but a different molecular mass number. Here the difference in mass number is due to the presence of a different number of neutrons. So, the isotopes are variants that have the same number of protons and electrons but different numbers of neutrons in particular elements. There are a total of three types of isotopes:

1. Stable isotopes: These isotopes are defined as the isotopes which have long half-lives (half-life is mainly a period in which the compound undergoes decomposition). Examples:
   • Carbon: Carbon-12, Carbon-13
   • Oxygen: Oxygen-16, Oxygen-17, Oxygen-18
2. Primordial isotopes: These isotopes possess primordial nuclei. These primordial nuclides have existed since our solar system was formed. As said that there are 339 naturally occurring isotopes on our earth. Out of 339 remaining 286 isotopes are primordial in nature.
3. Radioactive isotopes: Due to radioactive waves there are certain isotopes that have short lives and get decay rapidly by the emission. They are known as radioactive isotopes. Examples:
   • Chlorine: Chlorine-36
   • Uranium: Uranium-235 and Uranium-238

Ans. The atomic reactor is a device used to initiate and control nuclear fission chain reactions or nuclear fusion reactions. The main work of this reactor is to control nuclear fission, where atoms split and release energy. From the given diagram the parts of the reactor can be identified as:

• Fuel Fissionable materials like ⁹²U₂₃₅, ⁹²U₂₃₈, and ⁹⁴U₂₃₉ are used for fuel.
• To slow down fast neutrons, Moderator Heavy water, graphite and beryllium oxide are used.
• Coolant: The virus water, fluid oxygen, and others are used to eliminate heat produced in the parting interaction.
• Control bars: Cadmium or boron poles are used to safeguard neutrons to control the parting response.