Why do atoms emit radiation

Rory H. Feb 21, Explanation: The electrons in an atom can only occupy certain allowed energy levels. Related questions Does gravitational force get weaker with distance? How strong is gravitational force? How does cosmic background radiation change the universe? How does gravity affect the universe? If we take a neon sign and separate out the colors with a prism we would see the following spectrum:.

An observant student might now ask -- I see how light can produce colors now, but where does white light come from? The answer is that it comes from all the colors. When you take all the colors and combine them then you will get white. If we place sunlight or light from an incandecent lightbulb though a prism we would see the following spectrum:.

Now this spectrum looks different from the neon light because it is continuous. It is an entire band of light and not just several different lines.

The reason why this spectrum looks different is because it was not generated by electricity exciting particular gases. It was generated by heat exciting atoms. A substance coated on the inside of the glass absorbs the ultraviolet light and emits visible light.

Atoms are electrically neutral because:. However, an outer electron may absorb enough electromagnetic radiation to leave the atom entirely. When this happens, the atom becomes a positively charged ion. The process is called 'ionisation' - the atom has been ionised. Molecules can be ionised if one or more of their atoms become ionised.

Radiation that can ionise atoms and molecules is called ionising radiation. Being unstable does not lead an atomic nucleus to emit radiation immediately. Instead, the probability of an atom disintegrating is constant, as if unstable nuclei continuously participate in a sort of lottery, with random drawings to decide which atom will next emit radiation and disintegrate to a more stable state.

The time it takes for half of the atoms in a given mass to "win the lottery"--that is, emit radiation and change to a more stable state--is called the half-life. Half-lives vary greatly among types of atoms, from less than a second to billions of years. For example, it will take about 4. Iodine , commonly used in medicine, has a half-life of only eight days.

What is a radioactive decay chain? Stability may be achieved in a single decay, or a nucleus may decay through a series of states before it reaches a truly stable configuration, a bit like a Slinky toy stepping down a set of stairs. Each state or step will have its own unique characteristics of half-life and type of radiation to be emitted as the move is made to the next state.