Elements – Definition, Properties, Formation, Examples, Symbols

Everything around us is made of matter. Matter is composed of atoms, and atoms join together to form elements. These elements are the fundamental building blocks of all substances. There are over 100 known elements, each with unique properties.

Definition of Element

An element is a pure substance made up of only one type of atom. All atoms of an element have the same number of protons in their atomic nuclei. The number of protons is called the atomic number, which uniquely defines the element. For example, hydrogen has 1 proton, while carbon has 6 protons. Elements cannot be broken down into simpler substances by chemical means. Each element has distinct properties, which help us identify and study them.

Origin of the Elements

Elements are created through a variety of processes that occur in the universe, primarily during cosmic events. These processes include the Big Bang, stellar nucleosynthesis, neutron capture, and cosmic ray spallation.

1. Big Bang Nucleosynthesis

In the first few minutes after the Big Bang, the universe was extremely hot and dense. During this time, light elements were formed. The process primarily produced hydrogen (H), helium (He), and small amounts of lithium (Li). These light elements are the building blocks for everything that followed.

• Hydrogen became the most abundant element in the universe, and helium followed closely.
• Lithium, though present in trace amounts, was a product of this early formation process.

2. Stellar Nucleosynthesis

In the cores of stars, elements are created through nuclear fusion. Hydrogen fuses into helium via the proton-proton chain reaction. As stars age and become more massive, they begin to fuse heavier elements. This process continues until the formation of iron (Fe) in the core.

Fusion in stars: In stars, helium nuclei fuse with other helium nuclei and heavier atoms to form elements like beryllium (Be) and carbon (C):

This series of reactions continues as stars form heavier elements like oxygen (O), neon (Ne), and others up to iron. However, forming elements beyond iron requires different processes.

3. Neutron Capture Processes

To form elements heavier than iron, stars rely on neutron capture processes. These processes are essential for creating the heavier elements that we find in the universe today.

• s-process (slow neutron capture): This process occurs in aging stars, particularly red giants. In this process, neutrons are absorbed slowly, producing elements up to bismuth (Bi). These elements are created over long timescales and result in stable isotopes.
• r-process (rapid neutron capture): This process occurs during extreme cosmic events like supernovae and neutron star mergers, where a rapid influx of neutrons leads to the formation of heavy, neutron-rich elements like gold (Au), platinum (Pt), and uranium (U).

4. Cosmic Ray Spallation

Cosmic rays, which are high-energy particles that travel through space, can break apart heavier nuclei in the process known as spallation. This reaction produces lighter elements such as lithium (Li) and boron (B). While these elements are produced in small quantities, they play a crucial role in the element inventory of the universe.

Properties of Elements

Each element has its own unique properties, which can be categorized into physical and chemical properties.

Physical Properties

These can be observed without changing the element’s identity:

• State of Matter: Elements can be solid, liquid, or gas at room temperature.
• Density: This is the mass of the element per unit volume.
• Melting and Boiling Points: Every element has specific temperatures at which it melts or boils.
• Color: Some elements have distinct colors. For example, gold is yellow, and copper has a reddish-brown color.
• Conductivity: Elements like copper and silver conduct electricity well, while others, like rubber, do not.
• Hardness: Elements like diamond (carbon) are extremely hard, while others like sodium are soft.

Chemical Properties

These describe how elements react with other substances:

• Reactivity: Some elements, like sodium, react violently with water. Others, like gold, are highly unreactive.
• Acidity or Alkalinity: Some elements, like chlorine, form acids, while sodium creates alkalis.
• Oxidation: Elements like iron react with oxygen to form rust.
• Flammability: Hydrogen is highly flammable, while helium is not.

Examples of Elements

Elements are all around us and are found in various forms and compounds.

• Oxygen (O): Found in the air we breathe.
• Carbon (C): Present in all living things.
• Hydrogen (H): Part of water (H₂O) and many organic molecules.
• Iron (Fe): Used in construction and is present in blood to carry oxygen.
• Aluminum (Al): Commonly used in packaging and construction.
• Copper (Cu): Found in electrical wiring.
• Gold (Au): A precious metal used in jewelry and electronics.
• Silver (Ag): Known for its antibacterial properties.

Some elements exist in different states of matter at room temperature:

• Solids: Iron (Fe), Aluminum (Al), Carbon (C).
• Liquids: Mercury (Hg), Bromine (Br).
• Gases: Oxygen (O), Nitrogen (N), Helium (He), Neon (Ne).

Symbols of Elements

Each element has a unique symbol. These symbols are shorthand representations, usually one or two letters. The first letter is capitalized, and if there’s a second letter, it’s lowercase.

For example:

• H for Hydrogen
• C for Carbon
• O for Oxygen

Some symbols are derived from the Latin names of elements. For example:

• Fe for iron (from ferrum)
• Cu for copper (from cuprum)
• Na for sodium (from natrium)

The symbol of an element makes it easier to write chemical formulas. For example, the formula for water, H₂O, tells us that water consists of two hydrogen atoms and one oxygen atom.

How Elements Are Formed?

Here are element Formation Processes:

1. Fusion in Stars

Elements up to iron (Fe) are created in stars through a series of fusion reactions. The process starts with hydrogen, which fuses into helium. After that, successive helium fusion creates heavier elements, such as carbon (C), oxygen (O), and neon (Ne). Once iron is formed, the process stops, as iron cannot release energy through fusion.

2. Neutron Capture

As mentioned earlier, elements heavier than iron form through the s-process and r-process. These processes occur when neutrons are captured by atomic nuclei, creating heavier elements.

• s-process: Occurs slowly in red giants and produces stable elements like strontium-88.
• r-process: Happens rapidly in supernovae or neutron star mergers and produces neutron-rich isotopes, such as uranium-238.

3. Supernova Explosions

Supernovae are incredibly violent stellar explosions that disperse heavy elements into space. These elements become part of interstellar clouds that will later form new stars, planets, and other celestial bodies.

Geochemical Classification of Elements

Elements are also classified based on their behavior in Earth’s environment. They are categorized by how they bond with different Earth reservoirs, such as the core, mantle, crust, atmosphere, and biosphere.

1. Lithophile Elements

These elements bond with silicates and oxides. They are commonly found in the Earth’s crust and mantle. Examples include oxygen, silicon, and aluminum.

2. Chalcophile Elements

These elements bond with sulfur. They are commonly found in ores and are important for industrial applications. Examples include copper, zinc, and lead.

3. Siderophile Elements

These elements prefer to be in metallic cores. They tend to be found in the Earth’s core. Examples include iron, nickel, and platinum.

4. Atmophile Elements

These elements exist as gases in the atmosphere. They are essential for life. Examples include hydrogen, nitrogen, oxygen, and noble gases like helium and neon.

5. Biophile Elements

These elements are enriched in living systems. They form the building blocks of life. Examples include carbon, nitrogen, phosphorus, and sulfur.