# Nuclear equations

A nucleus changes into a new element by emitting or . These changes are described using nuclear equations.

Alpha decay (two and two ) changes the of the element by -4 and the by -2. An alpha particle is the same as a helium-4 .

### Example

$_{86}^{219}\textrm{Rn} \rightarrow _{84}^{215}\textrm{Po} + _{2}^{4}\textrm{He}$

Beta decay changes the atomic number by +1 (the nucleus gains a proton) but the mass number remains unchanged (it gains a proton but loses a neutron by ejecting an , so a beta particle is an electron).

### Example

$_{6}^{14}\textrm{C} \rightarrow _{7}^{14}\textrm{N}~+~_{-1}^{~0}\textrm{e}$

is pure energy and will not change the structure of the nucleus in any way.

Question

Uranium 238, $$_{92}^{238}\textrm{U}$$, emits an alpha particle to become what nucleus?

Alpha decay (two protons and two neutrons) changes the mass number of the element by -4 and the atomic number by -2 so the remaining nucleus will be $$_{90}^{234}?$$.

A periodic table shows that element number 90 is thorium, $$_{90}^{234}\textrm{Th}$$.

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