Nuclear equations
A nucleus changes into a new element by emitting nuclear radiations; these changes are described using nuclear equations.
Example
\(_{86}^{219}\textrm{Rn}\rightarrow _{84}^{215}\textrm{Po}\ +~_{2}^{4}\textrm{He}\)
Alpha decay (two nucleiNuclei is the plural of nucleus. The nucleus is the central part of an atom. It contains protons and neutrons, and has most of the mass of the atom. and two neutronUncharged subatomic particle, with a mass of 1 relative to a proton. The relative charge of a neutron is 0.) changes the mass numberThe number of protons and neutrons found in the nucleus of an atom. of the element by minus four and the atomic numberThe number of protons in the nucleus of an atom. Also called the proton number. by minus two. An alpha particle is the same as a helium-4 nucleusThe central part of an atom. It contains protons and neutrons, and has most of the mass of the atom. The plural of nucleus is nuclei..
Example
\(_{6}^{14}\textrm{C}\rightarrow _{7}^{14}\textrm{N}\ +~_{-1}^{0}\textrm{e}\)
Beta decay changes the atomic number by plus one (the nucleus gains a proton) but the mass number remains unchanged (it gains a proton but loses a neutron by ejecting an electronSubatomic particle, with a negative charge and a negligible mass relative to protons and neutrons., so a beta particle is an electron).
gamma radiationA type of ionising radiation that is also part of the EM spectrum. It has no mass. is pure energy and will not change the structure of the nucleus in any way.
Question
Uranium 238, 23892U, emits an alpha particle to become what nucleus?
Alpha decay (two protons and two neutrons) changes the mass number of the element by minus four and the atomic number by minus two so the remaining nucleus will be 23490.
A periodic table shows that element number 90 is thorium,23490Th.
Positron emission changes the atomic number by minus one (the nucleus loses a proton) but the mass number remains unchanged. Neutron emission does not change the atomic number but the mass number reduces by one.