Physics IIII

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Atomic structure

The atom consists of or three subatomic particles, protons, neutrons and electrons. Protons have a relative mass of 1 and a charge of +1. Neutrons have a mass of 1 and zero charge. Electrons have a negligible mass and -1 charge.

An atom has the same number of protons as electrons, so the number of negative charges balances out the number of positive charges and so the two cancel each other out which is why atoms are overal neutrally charged.

The mass number is the top number.

The atomic mass is the bottom number.

An ion is an atom with more or less electrons. As the number of protons and electrons will no longer be balanced the atom becomes an ion or a charged particle.

An isotope is an atom of the same element with the same number of protons but a different number of neutrons. It remains the same element as the proton number does not change.

The nuclei of some isotopes are unstable as they either have a large mass or as they have an extra neutron in their nucleus they are unstable. Unstable nuclei deca, spitting out particles and radiation. This is called radiactive decay. An isotope that does this is called a radioactive isotope. It can give out three types of radiation, Alpha, Beta or Gamma. If an isotope emits an alpha or beta particle its nucleus changed into that of a different element as the proton number, which determines which element an atom belongs to changes, and so the atom becomes that of a different element.

Alpha decay

An alpha particle is a helium nucleus consisting of 2 protons and 2 neutrons - it has a +2 charge. When a nucleus emits an alpha particle its mass decreases by 4 and its atomic number decreases by 2. As the proton number has changed it becomes the atom of a different element.

Beta decay

A beta particle is when a high energy electron is emitted from the nucleus. A beta particle occurs in the nucleus when a neutron changes into a proton and an electron in the nucleus. As electrons don't belong in the nucleus it is emitted out almost immidietly. Is a nucleus emits a beta particle then its mass number stays the same but the atomic mass increases by one.

Gamma decay

Gamma is a short wavelength from the electromagnetic specturm. When an unstable isotope emits an alpha or beta particle the nucleus moves around to get into a more stable position, when it does it releases excess energy in the form of a gamma ray. There is no mass or atomic number change when gamma is emitted.

Background radiation

Most background radiation comes from naturally occuring unstable isotopes. Background radiation comes from all around us, it occurs naturally in the air, in the food we eat and in rocks and building materials. Naturally occuring background radiation is the biggest contributer to the background radiation we recieve. We get a very small portion of…


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