What is an Atom ?

There are 92 different elements (atoms) in nature. Scientists have made the rest of them in the laboratory. The first one to be made was technetium, which has an atomic weight of 43.

The purest type of atom is called an element. Different types of atoms are called chemical elements, such as the Element Neon or the Element Gold. The exact size of the atom changes, depending on the element, see the Element Examples above.

The components of an atom are held together by three forces. Protons and neutrons are held together by the strong and weak nuclear forces. Electrical attraction holds electrons and protons.

There are three parts to an atom. Protons have a positive electrical charge and are found together with neutrons (no electrical charge) in the nucleus of each atom. Negatively charged electrons orbit the nucleus.

The nucleus is in the middle of the atom and contains protons, neutrons and electrons. These smaller particles of the atom - the protons, neutrons and electrons - all have different properties. Atoms must have equal numbers of protons and electrons.

While electrical repulsion repels protons away from each other, the attracting nuclear force is much stronger than electrical repulsion.

Atoms are the smallest particles that make up elements. Each element contains a different number of protons. For example, all hydrogen atoms have 1 proton while all carbon atoms have 6 protons. Some matter consists of one type of atom (e.g., gold), while other matter is made of atoms bonded together to form compounds (e.g., sodium chloride).

The strong force that binds together protons and neutrons is 1038 times more powerful than gravity, but it acts over a very short range, so particles need to be very close to each other to feel its effect.

All matter is made from particles called atoms. The Ancient Greeks described atoms as the smallest particles that make up everything. We now know that atoms are built from even smaller particles. Atoms link together and make MOLECULES.

The nucleus is in the middle of the atom and contains protons, neutrons and electrons. These smaller particles of the atom - the protons, neutrons and electrons - all have different properties. Atoms must have equal numbers of protons and electrons.

Atoms are mostly empty space. The nucleus of an atom is extremely dense and contains nearly all of the mass of each atom. Electrons contribute very little mass to the atom (it takes 1836 electrons to equal the size of a proton) and orbit so far away from the nucleus that each atom is 99.9% empty space. If the atom was the size of a sports arena, the nucleus would be the size of a pea. Although the nucleus is much denser compared with the rest of the atom, it too consists mainly of empty space.​

An atom a fundamental piece of matter.

The word "atom" comes from the Greek word for "uncuttable" or "undivided". The Greek Democritus believed matter consists of particles that could not be cut into smaller particles.

The radius of a typical atom is one tenth of a billionth of a meter. A string of atoms one meter (about 3 ft) long contains an atom for every person in the world. A cube of sugar contains as many atoms as there are stars in the Universe. The biggest atom (cesium) is nine times the diameter of the smallest atom (helium).

Atoms of a particular element contain the same number of protons. Protons are much larger and heavier than electrons and have a positive charge. Protons are positively charged and located in the nucleus together with the neutrons.

Everything in the universe (except energy) is made of matter,

There are over 100 different kinds of atoms. About 92 of them occur naturally, while the remainder are made in labs. The first new atom made by man was technetium, which has 43 protons. New atoms can be made by adding more protons to an atomic nucleus. However, these new atoms (elements) are unstable and decay into smaller atoms instantaneously. Usually, we only know a new atom was created by identifying the smaller atoms from this decay.

For a long time, people believed atoms were the fundamental "uncuttable" unit of matter. While atoms are the building blocks of elements, that can be divided into still smaller particles. Also, nuclear fission and nuclear decay can break atoms into smaller atoms.

The particles that make up atoms are electrons, protons, and neutrons. Their position in an atom is the ATOMIC STRUCTURE. Electrons are a kind of lepton. Protons and neutrons are made up of three quarks each. Quarks and leptons are fundamental particles—the smallest particles in the Universe.

The components of an atom are held together by three forces. Protons and neutrons are held together by the strong and weak nuclear forces. Electrical attraction holds electrons and protons. While electrical repulsion repels protons away from each other, the attracting nuclear force is much stronger than electrical repulsion. The strong force that binds together protons and neutrons is 1038 times more powerful than gravity, but it acts over a very short range, so particles need to be very close to each other to feel its effect.

Atoms are very small. The average atom is about one-tenth of a billionth of a meter across. The largest atom (cesium) is approximately nine times bigger than the smallest atom (helium)

Protons and neutrons are held together in the nucleus at the center of the atom by a strong force. But this force can be overcome by striking the nucleus with a neutron, a proton, or another particle. The nucleus may split and form new atoms. Atoms are split in this way inside nuclear reactors and during nuclear explosions.

Atoms of a particular element contain the same number of electrons. Electrons are tiny, very light particles that have a negative electrical charge. Electrons are negatively charged, circling the nucleus, making it a neutral, orbital particle.

everything in the universe is made of atoms.

The word "atom" comes from the Greek word for "uncuttable" or "undivided". The Greek Democritus believed matter consists of particles that could not be cut into smaller particles. For a long time, people believed atoms were the fundamental "uncuttable" unit of matter. While atoms are the building blocks of elements, that can be divided into still smaller particles. Also, nuclear fission and nuclear decay can break atoms into smaller atoms.