Chemical element

Everything is made of tiny bits.

These bits are called elements. They are all around you.

Each element has a special number. This number tells us what it is. For example, oxygen has the number 8. This number stays the same for every oxygen bit.

Some elements are found in nature. We can find gold in the ground. Most elements are found on Earth. There are 94 of these.

Some elements are made by people. Scientists make them in labs. There are 24 of these.

There are 118 elements known today. They are all very important. They make up our whole world.

Everything in our world is made of tiny bits called atoms.

A type of atom is called a chemical element.

Each element is defined by its number of protons. Protons are tiny parts inside the center of an atom. We call this number the atomic number. For example, oxygen has an atomic number of 8. This means every oxygen atom has 8 protons.

Atoms of the same element can have different numbers of neutrons. Neutrons are other small parts in the center. These different versions are called isotopes.

Scientists organize these elements in a special chart. This is the periodic table. A Russian chemist named Dmitri Mendeleev made the first version in 1869. The table puts elements in rows and columns. This helps us see how they act.

There are 118 known elements. The first 94 elements occur naturally on Earth. The other 24 are synthetic. Synthetic means people make them in labs using nuclear reactions. These reactions can change one element into another.

Everything in our universe is built from tiny building blocks called atoms.

A specific kind of atom is known as a chemical element. An element is defined by its atomic number. This number tells us how many protons live in the atom's center, or nucleus. For example, oxygen has an atomic number of 8. This means every oxygen atom has exactly 8 protons.

Atoms of the same element can also have different numbers of neutrons. These different versions are called isotopes. Even with different neutron counts, they stay the same element because the proton count does not change.

Atoms work together in many different ways to create the world. Some atoms join together to form molecules. For instance, hydrogen atoms can form a molecule called H2. When different elements join, they create chemical compounds. Water is a great example of this. Water is made of the elements hydrogen and oxygen.

Most elements on Earth are found as part of these mixtures or compounds. Only a few, like gold or platinum, are often found as pure, single elements. These elements can also be rearranged during chemical reactions to make something new.

Humans have been curious about these materials for a very long time. Early societies discovered native minerals like copper, sulfur, and gold. They did not yet understand the modern idea of an element. Later, people used ideas like alchemy to try to group materials.

A huge leap happened in 1869. A Russian chemist named Dmitri Mendeleev published the first recognizable periodic table. This table organizes elements by their increasing atomic number. It uses rows called periods and columns called groups. This special chart helps scientists predict how unknown elements might behave.

Today, we know of 118 different elements.

The first 94 elements occur naturally on Earth. These were present since the Solar System formed. The other 24 elements are synthetic. This means humans create them using nuclear reactions in a lab. Some of the newest ones were found recently. Element 118, called oganesson, was reported in October 2006. Element 117, called tennessine, was reported in April 2010. Some natural elements, like technetium, are very rare because they are unstable.

Understanding elements helps us see how the whole universe is connected. The very first elements, hydrogen and helium, were made during the Big Bang.

They were created in the first 20 minutes of the universe. Most other elements were made later through natural processes. Some are even made during massive events like supernovae. You can see these elements in the light from distant stars. Even the air you breathe is a mixture of elements like nitrogen and oxygen. Everything you touch is a result of these tiny, amazing particles.

A chemical element is a fundamental species of atom defined by its atomic number. This number represents the specific quantity of protons found within the atom's nucleus. For example, oxygen has an atomic number of 8, meaning every oxygen atom contains exactly 8 protons.

While the proton count defines the element, atoms of the same element can possess different numbers of neutrons. These variations are known as isotopes. Although isotopes have different masses, they maintain the same chemical properties because their electron counts remain identical. Almost all baryonic matter in the universe is composed of these elements, with rare exceptions like neutron stars.

The structure of an atom is central to how elements function. An atom consists of a dense nucleus containing positively charged protons and neutral neutrons. This nucleus is surrounded by a cloud of negatively charged electrons.

A force called the strong nuclear force holds the protons together, overcoming their natural electrical repulsion. Neutrons play a vital role here by providing stability. The ratio of neutrons to protons determines if a nucleus is stable or unstable. For instance, light elements like oxygen have a balanced ratio, but heavier elements like lead require more neutrons to stay together.

Elements can be categorized by their origin and stability. Currently, the International Union of Pure and Applied Chemistry (IUPAC) recognizes 118 elements.

The first 94 elements occur naturally on Earth, having been present since the formation of the Solar System. The remaining 24 elements are synthetic, meaning they are produced artificially through human-made nuclear reactions. Some natural elements are extremely rare because they are unstable. For example, technetium, promethium, astatine, francium, neptunium, and plutonium occur only in tiny trace amounts.

Understanding stability requires looking at radioactive decay. Some isotopes are "stable," meaning they do not decay over time. Others are "radioactive" or "unstable" and will eventually transform into other elements. This process is called decay and can happen through methods like alpha decay or beta decay. When an atom undergoes a nuclear reaction, its atomic number changes, effectively transforming it into a different element. Some of the heaviest elements, such as those with atomic numbers between 83 and 94, are unstable enough that their decay can always be detected. Even elements we consider stable, like lead, may be slightly radioactive with incredibly long half-lives.

The history of chemistry is a journey toward organizing these building blocks. Early human societies used native minerals like copper, sulfur, and gold without understanding their atomic nature.

Over time, theories like alchemy attempted to classify materials. A major breakthrough occurred in 1869 when the Russian chemist Dmitri Mendeleev published the first recognizable periodic table. He organized elements by increasing atomic number into rows called periods and columns called groups. This arrangement allowed scientists to see recurring physical and chemical properties. Mendeleev's table was so effective it allowed chemists to predict the existence of elements that had not yet been discovered.

Elements also exist in different physical forms and combinations. Two or more atoms can bond to create molecules. Some elements, like hydrogen, form diatomic molecules where two atoms of the same element join together.

When atoms of different elements combine, they form chemical compounds, such as water (H2O), which consists of hydrogen and oxygen. Most elements in nature are found as part of these compounds or mixtures rather than as pure substances. In fact, fewer than twenty elements, such as gold and platinum, are often found in nature as relatively pure native minerals.

The origins of the elements stretch back to the beginning of time. The lightest elements, hydrogen and helium, were created during Big Bang nucleosynthesis. This occurred within the first 20 minutes of the universe's existence.

These two elements were produced in a mass ratio of approximately 3:1. Most other elements were created later through various methods of nucleosynthesis. These processes happen in stars and during massive cosmic events like supernovae or neutron star mergers. By studying the light from these distant stars, scientists can identify which elements are present in the vast reaches of space.