Atomic spectra

To solve the puzzle of the atomic structure, we must study the atomic emission spectraWhite light is not actually white – it consists of many different colors. The composition of light – its spectrum – is studied by a device called a spectrometer

How to separate light: 

There are different ways to split white light into its different colors: 

One way is to use a Prism. Due to variations in Refractive Index, different colours follow distinct paths through the Prism, causing the colours to separate.

Another way is to use a so-called Diffraction grating, which consists of a large number of tiny grooves, placed parallel to each other on a surface.

On heating a mass of very closed atoms (solid, liquid or gas) to high temperature, it glimmers (radiates)

By examining the radiation we observe:

A rainbow of a mixed colors without any separation in between called (continuous spectra)

On heating gas or vapor substance (under reduced pressure) to high temperature or by electric spark, it radiates another type of radiation.By examining the radiation we observe:

A number of colorless lines (called line spectra)

Every element has its own unique line spectrum, its own electromagnetic fingerprint

The line spectra:

Consider as a characteristic for each element (just like finger print in human) because there is no 2 elements have the same spectral lines.
Can identify individual elements in complex mixtures of substances (by heating a sample of the substance and analyzing the resulting emitted light)
Can determine the elemental composition of far away bodies that emit light, like stars
Proved that sun composed of hydrogen and helium

As electrons move between the energy levels of an atom they can emit or absorb light energy.

If the electron is promoted, i.e. move from a lower energy level to a higher energy level, the atom must absorbs the energy exactly equal to the energy difference between the 2 energy levels (initial and final one)

E = Ef - Ei

When the electron falls from a higher energy lever to a lower energy level it will release the energy by emitting light with this energy. Since every kind of atom has a different electronic configuration, the wavelengths of light absorbed or emitted by an element are unique to that element. It is like an atomic fingerprint. The fingerprint recorded by measuring which types of light an atom absorbs is called the Atomic Absorption Spectrum. The fingerprint recorded by looking at which wavelengths of light an atom emits is called the Atomic Emission Spectrum. For gaseous atoms, these spectra will be a series of discrete "lines" of different colors (energies, wavelengths).