Subatomic particle

Subatomic particle

In physics, a subatomic particle is a particle smaller than an atom. These tiny pieces make up everything around us, from the air we breathe to the stars in the sky. According to the Standard Model of particle physics, subatomic particles can be either composite particles or elementary particles. Composite particles, like protons and neutrons, are made up of smaller parts. Elementary particles, such as electrons, are not made of anything smaller.

Scientists study these particles through special branches of science called particle physics and nuclear physics. They learn how these particles interact and work together to build the world we see. Some particles, like photons and gluons, carry forces but do not have weight when they are resting. These are called bosons. Other particles, called fermions, do have weight when resting and cannot share the same space.

Experiments show that light can act like a stream of particles, called photons, and also like waves. This idea is known as wave–particle duality. Another important idea is the uncertainty principle, which tells us that some properties of particles, like where they are and how fast they are moving, cannot both be known exactly at the same time. These discoveries help scientists understand the hidden world of tiny particles that make up our universe.

Classification

Subatomic particles are tiny pieces of matter that are smaller than atoms. They can be elementary (not made of smaller parts) or composite (made of more than one elementary particle bound together).

Elementary particles include several types: quarks, leptons, gauge bosons (which carry forces), and the Higgs boson. Composite particles, called hadrons, are made of quarks held together by particles called gluons. The most common hadrons are baryons (like protons and neutrons, which have three quarks) and mesons (which have two quarks). Most hadrons break apart very quickly, but protons and neutrons are stable and form the nuclei of atoms.

Other properties

All subatomic particles have electric charges that are whole number multiples of the smallest possible charge. Some particles, like quarks, have charges that are fractions of this smallest charge, but they cannot be seen alone because of a rule in physics.

Scientists have discovered that all particles behave like both particles and waves. This idea has been proven for tiny particles and even for larger things like atoms and molecules. Rules about how particles interact when they bump into each other help us understand how they behave, from the largest stars to the tiniest particles. These rules include keeping energy and movement steady, which are important ideas from old science books.

Dividing an atom

The electron is very light, about 1/1836 the weight of a hydrogen atom. Most of the hydrogen atom’s weight comes from the proton, which has a positive charge. The number of protons in an atom’s nucleus tells us what element it is. Neutrons have no charge and are a little heavier than protons. Different versions of the same element, called isotopes, have the same number of protons but different numbers of neutrons. The total number of protons and neutrons in an atom is called its mass number.

Chemistry looks at how electrons help atoms join together to form molecules and crystals. In nuclear physics, we learn how protons and neutrons fit together inside the tiny nucleus of an atom. To study these tiny particles, scientists use ideas from quantum mechanics and quantum field theory. This area of study is called particle physics, also known as high-energy physics because it needs a lot of energy to create new particles. This energy can come from cosmic rays or particle accelerators.

History

Main articles: History of subatomic physics and Timeline of particle discoveries

The word "subatomic particle" began being used in the 1960s to help organize many tiny pieces of matter. At first, scientists thought some small pieces called hadrons were simple. Later, they learned these pieces are made of even smaller parts.

Important discoveries in this area include many interesting finds over time.