if an atom's nucleus is unstable it can undergo a random process called radioactive decay it gives out radiation in order to become more stable there are different types of decay some atoms undergo alpha decay this happens if an atom has too few neutrons the atom releases an alpha particle made of two protons and two neutrons an alpha particle is the same as a helium nucleus a helium atom without its electrons alpha decay causes the atomic number of an atom to decrease by two because two protons are released the atomic mass decreases by 4 because two protons and two neutrons have been released for example an atom of oxygen 17 could release an alpha particle a helium nucleus or two protons and two neutrons this would also produce an atom of carbon 13. the element has changed because the number of protons has changed Alpha radiation has a low penetrating power so it's easily stopped by skin or as little as five centimeters of air however it does have a high ionizing power atoms will undergo beta Decay if they have too many neutrons a neutron turns into a proton and an electron this electron shoots out of the nucleus as a beta particle a beta particle is a high speed electron from the nucleus during beta Decay the atomic number increases by one because a new proton has been created from a neutron the mass number stays the same because even though an electron leaves the atom its mass is negligible so it doesn't affect the mass of the atom for example if an atom of oxygen 17 underwent beta Decay it would produce a beta particle an electron and an atom of fluorine 17. the element has changed because the number of protons has changed beta radiation has a higher penetrating power than Alpha so it's not stopped by air or skin but it is stopped by thick aluminum however it does have a lower ionizing power than Alpha radiation unstable nuclei may also emit gamma radiation in order to lose energy and become more stable a gamma ray is a wave of high energy electromagnetic radiation from the nucleus when an atom undergoes gamma Decay the atomic number and atomic mass both stay the same because no protons or neutrons have been emitted gamma has the highest penetrating power of the three types so thick lead is needed to stop it it also has the lowest ionizing power atoms can also emit a neutron this can happen naturally due to Cosmic reabsorption high up in the atmosphere or artificially which occurred when James Chadwick fired alpha particles at atoms of beryllium emitting a neutron won't change the element because the number of protons hasn't changed but the mass number will decrease by 1. so if oxygen 17 emitted a neutron it would produce a neutron and an atom of oxygen 16. here are some practice questions for you to try pause the video and give them a go an alpha particle is made of two protons and two neutrons which can also be called a helium nucleus a beta particle is a high-speed electron from the nucleus gamma radiation is high energy electromagnetic radiation emitted from the nucleus a beta particle is released when a neutron in the nucleus turns into a proton and an electron which is ejected from the nucleus at high speed the most ionizing type of radiation is Alpha and the most penetrating is gamma if uranium-235 decays by alpha decay the mass number will decrease by 4 and the atomic number will decrease by two the new isotope produced will be thorium-231 which has an atomic mass of 231 and an atomic number of 90. if carbon 14 undergoes beta Decay the mass number will stay the same but the atomic number will increase by 1 because a neutron has turned into a proton the new isotope that's formed is nitrogen 14 which has an atomic mass of 14 and an atomic number of seven thanks for watching I hope the video has been helpful for you and I'll see you in the next one