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# Glossary Physics

Subject: Physics
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### Atom:

An atom is the smallest particle that exists, everything is made of atoms. The word atom means indivisible.
Atom consists of a nucleus, protons (+), neutrons, (neutral), and electrons (-). Deep are the nucleus, composed of protons and neutrons and electrons that ultimately spins so fast that it looks like a shell. The number of protons, neutrons and electrons depends on what subject it is, but there is always the same number of protons as electrons, but it can vary how many neutrons there are in the nucleus of an atom.

### Mass:

The sum of protons and neutrons in the nucleus is the mass number. A certain mass number belongs to a certain kind of substance, thus can not be two different substances have the same mass number.

### Atomic number:

Number of protons in the nucleus determines how large atomic number is. There are never two different subjects with the same atomic number. If a substance has such 2 protons can be as Periodic Table see what subject it is.

### Elementary Particles:

An atom consists of three elementary particles, protons, neutrons, and electrons. The protons and neutrons in the nucleus while the electrons are around the nucleus and spins so fast that it looks like a shell.

### Isotopes:

Each atom has a specific atomic number, but all the same atoms need not have the same mass number. Some materials have in the nucleus, the same number of protons but different numbers of neutrons. They are called isotopes. Examples of an isotope is;

Some substances are radioactive, it means they give off dangerous radiation. The atoms of the radioactive substances that send out radiation when they fall into pieces. There are three types of radiation, alpha, beta and gamma radiation. All three are different strengths, large etc.
It was Henri Becquerel who first found natural radioactivity.
Alpha, beta and gamma radiation:
Alpha, beta and gamma radiation are three different kinds of radioactive radiations.
Alpha radiation consists of helium nuclei, two protons and two neutrons.
Alpha radiation atom, with its high speed knock off electrons if it hits another atom.
The atomic number decreases by 2 and the mass number by 4 when a nucleus emits an alpha particle. This changes the atom is left and it becomes a different substance than what it was before the particle alpha dispatched.
Beta radiation is composed of electrons. It is an electron that is sent out when an atom sends out beta radiation. Even when an atom emits beta radiation, it becomes a new subject. It is because there are protons and neutrons in the nucleus, neutrons transform into electrons and shipped. Then there is still more protons and less neutrons in the nucleus, where it has formed a new nucleus, thus a new topic.
Beta radiation is stronger and has longer range than alpha radiation.

### The gamma radiation

When a nucleus emits alpha and beta radiation is sent out simultaneously gamma radiation.
Gamma radiation is not made up of elementary particles, it is as tiny energy packets sent. It's the same kind of radiation as visible light, though invisible.
Gamma radiation is the strongest radioactive radiation, it can penetrate virtually everything except giant thick concrete walls or thick plates of metals, such as lead.

### Becquerel:

Henri Becquerel was the person who first found the natural radioactivity. In 1896, he put a rock containing uranium on a photographic plate, and when he then developed plate, he saw that it was black where the stone lay. He realized that he had discovered a then unknown radiation which he initially called "uranium radiation '.

Background radiation is radiation that do not come from a material, but it comes from the ground, from the house and from space. It is a radiation that we can not influence, but it's just there.

### Half-life:

A nucleus is radioactive can only emit radiation once, after the radiation sent out converted nucleus to another nucleus and it will be a different topic. The new subject will usually also radioactive.
If you have a topic that contains radioactive atoms have for a time half the atoms are converted into other substances emitted the radiation they had from the beginning, it is called half-life. After that it's been two half-lives have been the subject sent out half of the atoms was not deployed during the first half-life. Using the half-life can be calculated as how long a person has been dead or how many years some radioactive substances are not radioactive anymore.

### Chain reaction:

If you divide a uranium atom will charge less nuclei and some neutrons. The neutrons then assigns the second uranium atoms in different divisions. It becomes more and more neutrons that share more and more uranium atoms. See picture.

### Fission:

Fission mean splitting, when you shoot a neutron at a heavy uranium nucleus assigned to it. Of the formation of the two medium-heavy uranium nuclei and two loose neutrons and so released a large variety of existing nuclear energy. It allows one to use fission to different sources.

### Fusion:

Fusion is when such merge two hydrogen nuclei into helium nuclei. Many scientists dream of building a fusion reactor, which means that we get energy from when hydrogen nuclei into helium nuclei is that we can then use to what we now need energy. The good thing about it is that the helium produced is not as dangerous as the radioactive material from nuclear power plants today.

### Photos:

A photon is a light particle, it can be prepared when an atom is subjected to energy. When an electron pushed further out from the core, and then when it falls back towards the core, it can emit a light particle, a photon. Depending on how far the electron falls into the nucleus, it will be different colors on the photon. The bigger the case the photon becomes bluer.

### Ion:

If an atom, having about the same number of protons that electrons are more without becoming no longer an atom, but it becomes an ion. An ion is therefore either plus charged or minus charged.