Chemistry is the scientific study of the structure, properties, and changes that matter undergoes. At the foundation of chemistry are the concepts of atoms and elements. These basic units play a key role in understanding the chemistry of life, especially the composition and functioning of the human body. In this note, we will discuss the basic structure of an atom, the difference between atoms and elements, the main elements in the human body, and the role of isotopes and radioisotopes in chemistry.
Atoms and atomic structure
Atoms are the smallest units of matter that retain the chemical properties of an element. Atoms are made up of three main subatomic particles: protons, neutrons, and electrons.
- proton A positively charged particle found in the nucleus of an atom. It has a mass of approximately 1 atomic mass unit (amu). The number of protons in an atom defines an element and is called its atomic number. For example, every carbon atom has 6 protons.
- neutron Neutrons are neutral particles (particles with no electric charge) found in the nucleus of an atom. They are slightly larger than a proton and have a mass of about 1 amu. Neutrons contribute to the atomic mass but do not affect the charge of the atom.
- Electronic Electrons are negatively charged particles with negligible mass compared to protons and neutrons. Electrons orbit the nucleus in regions called electron shells. Despite their extremely small mass, electrons play an important role in chemical bonds and chemical reactions.
The nucleus, containing the protons and neutrons, is very dense compared to the relatively large electron shells. Most of the atom’s mass is concentrated in the nucleus, while the electrons are spread out over a large volume.
Electron shell
The classical model of an atom describes electrons as orbiting a nucleus, similar to planets orbiting the sun. However, this is a simplification. Electrons exist in probability regions called electron shells. The first shell can hold up to 2 electrons, the second shell up to 8, and the third shell up to 18. Electrons fill the lowest energy levels (or shells) first before occupying higher levels (or shells). This arrangement affects how atoms interact chemically.
Atoms and Elements
The terms “atom” and “element” are often used interchangeably, but they have different meanings.
- atomAtoms are the smallest units of elements that retain chemical properties. Atoms are made up of protons, neutrons, and electrons. Atoms combine to form molecules, which are the building blocks of matter.
- elementAn element is a pure substance that consists of only one type of atom. An element is defined by its atomic number, or the number of protons it contains. For example, hydrogen (H) is an element that has an atom with one proton. There are currently 118 known elements, each with their own unique properties.
The main elements that make up the human body
The human body is mainly composed of several important components that are essential for various biological functions.
- Oxygen (O)Oxygen makes up about 65% of the human body’s mass and is essential for cellular respiration, the process by which cells produce energy.
- Carbon (C)Carbon makes up about 18% of our bodies and forms the backbone of organic molecules such as carbohydrates, proteins, lipids, and nucleic acids.
- Hydrogen (H)Hydrogen makes up about 10% of the body’s water and, as a component of water and organic molecules, plays an important role in maintaining pH balance and producing energy.
- Nitrogen (N)Nitrogen makes up about 3% of the body and is an important component of amino acids, the building blocks of proteins, and nucleic acids, which make up DNA and RNA.
Other elements such as calcium, phosphorus, potassium, sulfur, sodium and magnesium, although present in smaller amounts, are essential for maintaining health and supporting various physiological functions.
Atomic number, mass number, isotope, radioisotope
To understand the differences between atoms, we need to distinguish between atomic numbers, mass numbers, isotopes, and radioisotopes.
- Atomic NumberAtomic number is the number of protons in the nucleus of an atom. The atomic number determines the element and its position on the periodic table. For example, carbon has an atomic number of 6, which means that every carbon atom has 6 protons.
- Mass numberMass number is the sum of the protons and neutrons in an atomic nucleus. It represents the total mass of the nucleus. For example, carbon-12 has a mass number of 12, indicating that it has a total of 6 protons and 6 neutrons.
- IsotopesIsotopes are different elements of the same element that have the same number of protons but different numbers of neutrons, which gives them different mass numbers. For example, carbon has three isotopes: carbon-12 (6 protons and 6 neutrons), carbon-13 (6 protons and 7 neutrons), and carbon-14 (6 protons and 8 neutrons).
- Radioisotopes: A radioisotope is an unstable isotope that decays over time, emitting radiation in the process. This radioactive decay changes the isotope into a more stable form. Radioisotopes are used in a variety of applications, including medical diagnosis and treatment. For example, iodine-131 is used to treat thyroid disorders.
Isotope production
Isotopes are produced through a variety of nuclear processes.
- Natural ProcessesSome isotopes occur naturally: carbon-14, for example, is produced continually in the atmosphere by the interaction of cosmic rays with nitrogen-14.
- Artificial ProcessesIsotopes can also be created artificially in a laboratory or nuclear reactor. By bombarding stable atoms with neutrons and other particles, scientists can create isotopes with different mass numbers. For example, technetium-99m, which is used in medical imaging, is created in a nuclear reactor.
Conclusion
Understanding basic concepts of atomic structure, the distinction between atoms and elements, and the role of isotopes and radioisotopes are fundamental to chemistry and are essential for exploring the chemistry of life. These concepts help elucidate the composition and function of biological molecules and the use of radioactive materials in medicine. Understanding these principles provides insight into how the smallest units of matter contribute to the complex processes that sustain life.
