Science question(s)

[shlin28]

In a chemistry lesson my teacher explained that in transition metals the electrons recieve enough energy from light, so they "jump" up an energy level and back down, producing light energy, hence producing colour. It also happens in other elements but they would require more energy in order to make them produce a colour, hence burning some substances gives a pretty flame, apparently. The teacher didn't explain anymore because the class was getting confused, but I am interested in the following:

1. If there are no light, does that mean transition metals, and in turn all compounds containing them, would all be black? as they would not produce any colour?

2. The stars are obviously blue/green/red/orange etc, is it because the electrons are recieving so much energy that they jump up and down so fast that it is of that colour, or is it because of some strange properties atoms have because they are plasma?

[TevashSzat]

1) Well, color is due to the presence of light so if there were no light, no atoms would have color unless they are naturally giving off protons due to some form of radiation or something like that

2) Fusion within the star's core produce gamma ray photons which release as ultraviolet rays, visible light, and a host of really nasty radiation.

Difference in color is due to the relative temperature of the star's surface which is in turn due to the rate of fusion within the core

[Avicenna]

1) Colour isn't only produced due to energy transitions of electrons. For example, some compounds' colours are due to the way they cause light to refract and the interference which occurs as a result

And I think you've misunderstood the teacher. The transition metal doesn't "produce" light as it were. It absorbs the photons of one energy, then scatters it again in a random direction, so, for our intents and purposes, we can imagine that that's been removed from the spectrum. So the original white light you shine on it is no longer white, but coloured.

2) It's due to the Wien's displacement law, in particular this graph.

The different stars are all at different temperatures.
Hence different parts of the visible spectrum dominate:
- if all red, blue and green are roughly equal, the star appears white
- if there is only a small tail into the visible region from the IR side, it appears red
- if the same happens from the UV side, it appears blue

Both of you are correct: it's due to the collisions giving enough energy to promote electrons to higher orbitals. When they drop down, they release photons of energy corresponding to E=hf.

Hope I've been of some help

[Ibrahim]

In a chemistry lesson my teacher explained that in transition metals the electrons recieve enough energy from light, so they "jump" up an energy level and back down, producing light energy, hence producing colour. It also happens in other elements but they would require more energy in order to make them produce a colour, hence burning some substances gives a pretty flame, apparently. The teacher didn't explain anymore because the class was getting confused, but I am interested in the following:

1. If there are no light, does that mean transition metals, and in turn all compounds containing them, would all be black? as they would not produce any colour?

no-color is due to light wavelength being absorbed and/or reflected. e.g. green is the result of the green object absorbing every visible wavelength exept green's

2. The stars are obviously blue/green/red/orange etc, is it because the electrons are recieving so much energy that they jump up and down so fast that it is of that colour, or is it because of some strange properties atoms have because they are plasma?

no, it is of any particular color because it emits that particular visible light color the most. a star that emits very high amaounts of UV or X-ray will appear violet, because the emission will follow a peak patter round the most heavily emitted spectrum (ie violet will be the most emited visible light). however, there is a correlation between temperature and color, wit the hottest being the most violet.

EDIT: ow, avecinna answered it well.