Changes in atoms and the nuclei of atoms can result in electromagnetic…

The idea

Electromagnetic waves come out of atoms in two different ways. Changes in the electrons of an atom, where an electron moves between energy levels, produce waves in the infrared, visible, ultraviolet and X-ray parts of the spectrum; this is why a hot filament glows and why a fluorescent coating gives out visible light after absorbing ultraviolet. Changes inside the nucleus produce gamma rays, which sit at the highest frequency end. The process runs both ways: an atom can absorb a wave of the right frequency and move to a higher energy level, which is exactly what ozone does with ultraviolet. Because the energy changes available range from very small to very large, the frequencies generated and absorbed cover a very wide range.

What earns the marks

• Saying that changes in the electron arrangement of an atom generate or absorb electromagnetic waves.
• Saying that changes in the nucleus generate gamma rays.
• Stating that absorption as well as emission can occur.
• Linking a larger energy change to a higher frequency of the wave produced.

Common mistakes and how to put them right

• Saying gamma rays come from the electrons of an atom.

• Treating emission and absorption as separate processes that happen in separate materials.

• Saying X-rays come from the nucleus, when they come from electron transitions or decelerating electrons.

• Claiming that only radioactive atoms emit electromagnetic waves.

Exam tips

• Keep the two sources clearly separate: electrons for most of the spectrum, the nucleus for gamma rays.
• If the question mentions a nucleus, the answer will involve gamma rays.
• Use the word absorbed as well as emitted when the statement covers both.