• Question: What causes different elements to have different spectrums?

    Asked by amyjohns to Adam, Catherine, Karen, Leila, Nazim on 15 Mar 2012.
    • Photo: Leila Battison

      Leila Battison answered on 12 Mar 2012:

      The spectra of elements comes from the numbers and the amount of energy that their electrons have. The more electrons, the further they are from the positive nucleus, the more energy they have, and the brighter the colours on the spectrum!

    • Photo: Adam Stevens

      Adam Stevens answered on 12 Mar 2012:

      The spectrum of an element is due to the arrangement of its electrons. Each element has a different arrangement.

      The spectrum we see if caused by electrons moving up and down in the shells around the nucleus of the element, so the arrangement of the electrons determines which ones can move up and down.

      The spectrum of each element consists of a number of lines of colour created by these electrons moving up and down. Some elements have more lines that others, but by looking at the lines we can tell what the element is.

      For example, Sodium has two very strong yellow lines close together, so we can identify sodium very easily.

    • Photo: Catherine Rix

      Catherine Rix answered on 12 Mar 2012:

      Elements have shells of different energy which can contain electrons. When an atom is excited (gains energy) electrons can move into a higher energy level. The extra energy can be lost by emission of electromagnetic radiation. The wavelength of the emitted light is dependent on the difference in energy between the electron shells, which is different for different elements.

    • Photo: Karen Masters

      Karen Masters answered on 15 Mar 2012:

      Elements are made up of atoms – which have a nucleus (of protons and neutrons) and electrons. The electrons can get removed from the atoms in something called “ionization” and each atom needs a specific amount of energy to remove its electrons (you can get rid of all of them in turn). The spectral lines you see from an element are a signature of these energies. You can also sort of partially remove an electron (sort of like taking it one step towards being removed) and those steps have specific energies (so spectral lines) associated with them for each different element too.

      It’s very useful that this happens for astronomers. For most things we study we can only look at them – so we can use this information to decode the light we see coming from a star for example, and figure out which elements and how much of each element are in the star.

    • Photo: Nazim Bharmal

      Nazim Bharmal answered on 15 Mar 2012:

      The spectrum is actually one of the best pieces of information we have about how the atoms of elements behave. The most important thing it depends on is how far away electrons orbit the nucleus of the element’s atoms. That distance depends on how many neutrons and protons there are in the nucleus.

      A critical part of the spectrum is at radio frequencies, where at 21 cm (I think) Hydrogen emits radio signals. We can measure this with radio telescopes on Earth to see where Hydrogen exists in the universe, and since that is the most basic element that stars need to form, we can use that radio signal to find where galaxies may be forming new stars.

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