Subatomic Particles, Carbon Isotopes, and Radioactive Decay

Elements and Atoms:
- Each element, such as carbon, consists of atoms that are unique and distinct from the atoms of any other element.
- An atom is defined as the smallest unit of matter that retains all the chemical properties of an element.
Subatomic Particles:
- Atoms are composed of smaller constituent units termed subatomic particles.
- Biological studies focus primarily on three key subatomic particles: neutrons, protons, and electrons.
The Atomic Nucleus:
- Neutrons and protons cluster together to form the atomic nucleus at the center of the atom.
- In a carbon atom, the nucleus contains $6$ neutrons and $6$ protons.
- Because neutrons possess no electrical charge and protons carry a positive charge, the atomic nucleus maintains an overall positive electrical charge.
- Neutrons and protons have almost identical mass.

Electrical Charges of Subatomic Particles:
- Neutrons: Carry no electrical charge (neutral).
- Protons: Carry a positive electrical charge ( $+$ ).
- Electrons: Carry a negative electrical charge ( $-$ ).
Structure and Behavior of Electrons:
- Electrons form a cloud of negative charge surrounding the positively charged atomic nucleus.
- Electrons are held within this cloud structure due to their attraction to the positively charged protons in the nucleus.
- Electrons are extremely small, possessing a mass of approximately $\frac{1}{2000}$ of the mass of a proton.
- The significantly lower mass of electrons allows them to move rapidly around the nucleus compared to the slower movement of protons and neutrons.

Proton Constancy and Elemental Identity:
- All atoms of a given chemical element contain the exact same number of protons.
- Elements are sorted and identified specifically by their proton count.
Definition of Isotopes:
- While all atoms of an element share the same number of protons, they may differ in their number of neutrons.
- Isotopes are defined as these different atomic forms of a single element.
- Despite having different atomic masses due to varying neutron counts, all isotopes of an element behave identically in chemical reactions.

General Characteristics of Carbon Isotopes:
- Carbon has three naturally occurring isotopes.
- All three carbon isotopes contain exactly $6$ protons, which preserves their identity as carbon.
Specific Carbon Isotopes:
- Carbon-12 ( $^{12}\text{C}$ ):
- The most common naturally occurring isotope of carbon.
- Accounts for approximately $99\%$ of the carbon found in nature.
- Contains $6$ protons and $6$ neutrons.
- Classified as a stable isotope (does not lose subatomic particles or undergo decay).
- Carbon-13 ( $^{13}\text{C}$ ):
- Contains $6$ protons and $7$ neutrons.
- Classified as a stable isotope (does not undergo decay).
- Carbon-14 ( $^{14}\text{C}$ ):
- Contains $6$ protons and $8$ neutrons.
- Classified as an unstable or radioactive isotope.

Nature of Radioactive Isotopes:
- Radioactive isotopes are unstable and undergo spontaneous decay over time.
- During decay, radioactive isotopes emit particles and energy.
Mechanism of Carbon-14 Transmutation:
- During the decay of carbon-14, one of its $8$ neutrons spontaneously converts into a proton.
- The neutron count decreases from $8$ to $7$ , while the proton count increases from $6$ to 7$.\n - This conversion alters the atomic identity of the particle because elemental identity is governed by proton count.\n - The resulting atom with 7 $protons is no longer carbon, but has transmuted into nitrogen ($ \text{N}$$).

Research Applications in Biology:
- Fossil Dating: Carbon-14, along with other radioactive elements, is used to estimate the age of ancient fossils.
- Metabolic Tracing: Radioactive isotopes function as tracer molecules to track the pathway of specific atoms through biological and metabolic processes.
Medical Diagnostics:
- Radioactive isotopes are utilized to diagnose medical conditions, such as Graves' disease.
- Diagnostic Procedure: Medical evaluation measures the rate of radioactive uptake of specific elements within targeted organs, such as the thyroid gland.
- Clinical Marker: A higher level of radioactive uptake in the thyroid indicates the presence of Graves' disease in a patient.
Health Hazards of Radiation:
- Radiation emitted from decaying radioactive isotopes poses significant hazards to biological life.
- Decaying isotopes emit radiation that damages cellular molecules.