The actvity of a radioactive sample only depends on the number of unstable nuclei present. The radioactivity of a material decreases over time because the amount of radiocative nuclei decreases. When a radioactive nucleus emits an alpha or beta particle, the number of protons and neutrons changes and it becomes a new element. Once atoms are ionised by radiation and form ions, these charged ions can break and make chemical bonds, therefore changing molecular structure. Ions can interfere with the structure of DNA, causing it to behave incorrectly and damage living cells. Oxygen, hydrogen, nitrogen and carbon are highly susceptible to ionisation and are abundant in the body. One Sievert of alpha, beta or gamma produces the same biological effect, and is a measure of the possible harm done to your body. The unit of radiation absorbed equivalent dose is the Sievert (Sv). Beta and gamma are much more penetrating and will pass through skin, so are more dangerous outside the body, despite being poorer ionisers. Inside the body, alpha particles would be highly damaging, but are relatively safe outside the body. Low intenisty radiation can affect the cell's genetic makeup, causing mutations that could lead to cancer.Īlpha particles are large and highly ionising, but do not pass through the skin. Some high intensity radiation causes cells to become sterile (containing no living organisms). High intensity radiation may kill the living cells and cause tissue damage, and could lead to radiation sickness. Ionising radiation collides with living cells and knocks electrons out of the atoms, leaving positive ions. The damage depends on the type and intensity of the radiation. Ionising radiation can damage living cells. Isotopes are atoms of the same element with the same number of protons but differing numbers of neutrons in the nucleus. The number of protons in a nucleus determines the element and its chemical properties.

It has to balance the repulsive electrostatic force between the protons. The conclusions were that most of an atom is simply empty space since most particles passed straight through the mass and charge of an atom is concentrated in a small area in the centre of the atom (the nucleus) the nucleus is positive since the positive alpha particles were repelled.Ī strong nuclear force holds the protons and neutrons in the nucleus together. The observations recorded were that most alpha particles passed striaght through the gold foil undeviated a few particles were deflected through small angles and even fewer bounced straight back from the foil. Nearly all the mass of the atom is concentrated in the nucleus.Įvidence about the structure of the atom from the 1909 Rutherford-Geiger-Marsden alpha scattering experiment during which alpha particles were fired at gold foil. An atom is neutral so has an equal number of electrons and protons. Neutrons have the same mass as protons and have no charge. Protons have a mass 2000 time that of an electron and are positively charged. Electrons are the smallest particle and are negatively charged. Electrons orbit the nucleus at high speed. Neutrons and protons form the nucleus of an atom. An atom is the smallest part of an element.

Chemteam fission uranium