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Atoms are the basic units of matter and are made up of smaller components called subatomic particles. There are many types of subatomic particles known to science, but in the context of basic atomic structure, only three are considered most important: electrons, protons and neutrons. These three particles differ in their location, charge and mass. Together, electrons, protons and neutrons form the complete structure of atoms. Their arrangement and interaction define the atom's properties, chemical behavior, and participation in physical and chemical processes. These subatomic particles laid the foundation of modern atomic theory and quantum chemistry. 1. Electron Electrons are negatively charged subatomic particles. They are extremely small in mass and are found outside the nucleus of the atom in specific regions called orbitals or shells. The charge of an electron is −1  and its mass is approximately 1/1836 of a proton or neutron, which is around 9.1 × 10⁻³¹ kg, meaning it is n...

Electromagnetic radiation is a form of energy that travels through space in the form of waves created by the motion of electrically charged particles. When such a charged particle accelerates, meaning its speed or direction changes, it gives rise to oscillating electric and magnetic fields. These two fields are always perpendicular to each other and also to the direction in which the radiation travels. This kind of energy does not need any material medium to move. It can travel through empty space (vacuum) as well as through transparent substances like air, glass or water. The theory of electromagnetic radiation was first proposed by the Scottish physicist James Clerk Maxwell in the year 1865. According to his theory, electromagnetic radiation is produced by the simultaneous propagation of electric and magnetic fields. These fields move together as waves and carry energy from one place to another. This combined wave is called an electromagnetic wave  and it is the basic form i...

A chemical element is a pure substance made up of only one type of atom, which is defined by its atomic number, i.e., the number of protons in the nucleus of each atom. This atomic number gives the element its identity and distinguishes it from all other elements. For example, carbon always has six protons, so its atomic number is 6. All substances found in nature, whether living or non-living, are made up of chemical elements or their compounds. These elements serve as the building blocks of all matter. For example, water is made from hydrogen and oxygen, rocks are made from silicon, oxygen, aluminum, etc., and living organisms are made mostly from carbon, hydrogen, oxygen, and nitrogen. So far, 118 chemical elements have been discovered, out of which 94 occur naturally. The remaining are artificially synthesized in laboratories. Among these, 80 elements have stable isotopes. All elements with atomic numbers 1 to 82 have at least one stable isotope, except technetium (43) an...

The human body is made up of various chemical elements that work together to support life. These elements are not just part of the body's physical structure like bones, muscles and skin but also control important functions such as breathing, digestion, nerve signaling and cell repair. Most of these elements combine to form molecules like water, proteins, fats, carbohydrates and nucleic acids which are the foundation of life. Although more than 60 elements are present in the body, only some of them are truly essential for survival and good health. These essential elements are grouped into three categories based on how much of them is present in the body: major elements, minor elements and trace elements. Each element, whether present in large or tiny amounts, has a special role in maintaining the structure and working of the human body. 1. Major Elements (Bulk Elements) There are six major elements that form about 98% of the total body mass. These elements are oxygen, carbon, hydrog...

The Earth's atmosphere is a layer of gases that surrounds the planet and is held in place by gravity. This gaseous envelope plays a vital role in supporting life by providing oxygen for respiration, carbon dioxide for photosynthesis and protection from harmful solar radiation. It also regulates temperature, helps in weather formation and maintains pressure balance necessary for survival. The atmosphere is composed of a mixture of different elements and compounds, each present in specific proportions. Some of these gases are present in large quantities while others occur in very small traces. However, even those present in minute amounts can have significant environmental or biological roles. The composition of the atmosphere is generally stable up to around 80 to 100 kilometers from the Earth's surface and this region is known as the homosphere where gases are well mixed. The major components of this layer are nitrogen, oxygen and argon, while several other gases like carbon d...

The ocean water of Earth is not made up of just pure water but is a complex mixture of various chemical elements. These elements exist either as part of water molecules or as dissolved ions and gases. The majority of ocean water is composed of oxygen and hydrogen, which form the water molecule (H₂O), but in addition to these, several other elements are present in small to trace amounts. These elements come from various natural sources like river runoffs, volcanic eruptions, seafloor weathering and atmospheric deposition. Some of them like sodium, chloride, and magnesium contribute to the salinity of seawater, while others like carbon, sulfur, and calcium play important roles in oceanic biological and chemical cycles. The elemental composition of ocean water by mass gives a clear idea about which elements dominate in the ocean and which are present in minor or trace amounts but still remain essential for marine life and geochemical balance. 1. Major Elements (more than 1% by mass) Th...

The Earth's crust is the thin, outermost solid layer of our planet which forms both the continents and the ocean floors. It lies above the mantle and makes up less than 1% of Earth's total volume but it is the most accessible and studied layer because all landforms, soils and rocks we see are part of the crust. The crust is composed mainly of solid rocks and minerals, which in turn are made from various chemical elements. These elements do not exist in pure form but are combined in complex compounds like silicates, oxides, carbonates etc. Although more than 90 naturally occurring elements are found in the crust, only a small group of them dominate its total mass. The composition of the crust reflects its geochemical origin, its formation history and the processes like weathering, erosion, and plate tectonics that continuously shape it. Each of these elements has specific roles in rock formation and Earth’s surface structure. Their proportions are usually expressed by mass pe...

Biomolecules are natural chemical compounds that are found inside all living organisms. These molecules are essential for life. They form the structure of cells and carry out various biological functions such as producing energy, building tissues, storing information and regulating reactions. Without biomolecules, life cannot exist. Biomolecules are mostly organic, which means they are made of carbon atoms along with hydrogen, oxygen, nitrogen, phosphorus and sulfur. These elements combine in different ways to form molecules that help the cell survive, grow and reproduce. All organisms, from the smallest bacteria to large animals and plants, are made of biomolecules. The chemical structure of biomolecules is mostly the same in all living organisms. For example, glucose found in humans and in plants is exactly the same molecule. This shows that biomolecules are universal in nature and conserved through evolution. Major Types of Biomolecules Biomolecules are mainly divided into f...