Atomic physics facts for kids
Atomic physics is a part of physics that looks closely at atoms. It studies atoms as if they are alone, focusing on their tiny parts: the electrons and the atomic nucleus.
This field mainly explores how electrons are arranged around the nucleus. It also studies how these arrangements can change. This includes both neutral atoms and ions (atoms with an electrical charge). When we say "atom" here, we usually mean both.
Sometimes, people confuse "atomic physics" with nuclear power or nuclear bombs. This is because the words "atomic" and "nuclear" are often used to mean the same thing in everyday talk. However, physicists see them differently. Atomic physics deals with the whole atom, including its nucleus and electrons. Nuclear physics, on the other hand, only studies the nucleus itself.
It can be hard to draw a strict line between different science fields. Atomic physics is often seen as part of a bigger area called atomic, molecular, and optical physics. Many science groups that do research are organized this way.
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What are Isolated Atoms?
Atomic physics always looks at atoms as if they are by themselves. Models of atoms usually show a single nucleus with one or more electrons orbiting it. This field does not study how molecules are formed. It also doesn't look at atoms in a solid state, like in condensed matter.
Instead, atomic physics focuses on processes like ionization (when an electron leaves an atom) and excitation (when an electron gains energy). These changes can happen when atoms interact with light (photons) or crash into other tiny particles.
You might think studying atoms alone isn't very realistic. But if you think about atoms in a gas or plasma, they spend most of their time far apart. The time they interact with each other is very short compared to the changes happening inside the atom. This means we can treat individual atoms as if they are alone most of the time. Because of this, atomic physics helps us understand plasma physics and atmospheric physics, even though these fields deal with huge numbers of atoms.
How Electrons are Arranged
Electrons move in what we can imagine as "shells" around the nucleus. Normally, electrons are in their lowest energy state, called the ground state. But they can get excited if they absorb energy. This energy can come from light (photons), magnetic fields, or collisions with other particles (like other electrons).
When electrons are in a shell, they are in a bound state. The energy needed to completely remove an electron from its shell is called the binding energy. If an electron absorbs more energy than its binding energy, the extra energy turns into kinetic energy (movement energy). When this happens, the atom has gone through ionization.
If an electron absorbs less energy than its binding energy, it moves to a higher energy level, called an excited state. After some time, an electron in an excited state will usually drop back to a lower energy state. When it does, the atom must release the extra energy. In a neutral atom, this energy is given off as a photon (a tiny packet of light).
However, if the excited atom has already lost an electron (is an ion), something else can happen. This is called the Auger effect. The energy from the excited electron is transferred to another electron in the atom. This other electron then gets enough energy to leave the atom. This way, one photon can cause an atom to lose more than one electron.
There are strict rules about which electron arrangements can be reached by absorbing light. But there are no such rules when electrons get excited by collisions with other particles.
History of Atomic Physics
Like many areas of science, physics has both theoretical work (ideas and math) and experimental work (testing things). Atomic physics is the same. Often, progress happens in cycles: an experiment shows something new, then scientists try to explain it with a theory. This theory might then predict new things that experiments try to confirm. What scientists can do depends on the technology available at the time. So, it can take a long time for theories to be fully developed.
One of the first big steps in atomic physics was realizing that all matter is made of "atoms." These are the basic units of a chemical element. John Dalton, a British chemist and physicist, developed this idea in the 18th century. Back then, scientists didn't know exactly what atoms looked like inside. But they could describe and sort them based on their properties, like in the periodic table.
The real start of atomic physics came with the discovery of spectral lines. These are specific colors of light that atoms give off or absorb. Scientists like Joseph von Fraunhofer tried to explain them. Studying these lines led to the Bohr atom model and the beginning of quantum mechanics. To explain atomic spectra, a completely new mathematical way of understanding matter was found. This led to a better description of atoms and their electron shells, known as the atomic orbital model. It also gave a new scientific basis for chemistry (quantum chemistry) and spectroscopy (the study of light and matter).
Since World War II, both theoretical and experimental atomic physics have grown very quickly. This is thanks to advances in computer technology. Computers allow scientists to create bigger and more complex models of atoms and how they interact. New technologies like particle accelerators, detectors, strong magnets, and lasers have also greatly helped experimental work.
Important Atomic Physicists
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Related pages
- Particle physics
- Isomeric shift
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See also
In Spanish: Física atómica para niños
