Download Atomic emission spectrum

Atomic emission
spectrum
 When a sample of gaseous atoms of an
element at low pressure is subjected to an
input of energy, such as from an electric
discharge, the atoms are themselves found to
emit electromagnetic radiation.
 On passing through a very thin slit and then
through a prism the light (electromagnetic
radiation) emitted by the excited atoms is
separated into its component frequencies.
 The familiar dispersion of white light is
illustrated below:
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 Solids, liquids and dense gases glow at high
temperatures. The emitted light, examined using a
spectroscope, consists of a continuous band of colours
as in a rainbow. A continuous spectrum is observed.
This is typical of matter in which the atoms are packed
closely together. Gases at low pressure behave quite
differently.
 The excited atoms emit only certain frequencies, and
when these are placed as discreet lines along a
frequency scale an atomic emission spectrum is
formed.
 The spectral lines in the visible region of
the atomic emission spectrum of barium
are shown below.
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 The atomic emission spectrum of an element is the set of
frequencies of the electromagnetic waves emitted by atoms of that
element. Each atom's atomic emission spectrum is unique and
can be used to determine if that element is part of an unknown
compound.
 Light consists of Electromagnetic radiation of different
wavelengths. Therefore, when the elements or their compounds
are heated either on a flame or by an electric arc they emit energy
in form of light. Analysis, of this light, with the help of spectroscope
gives us a discontinuous spectrum. A spectroscope or a
spectrometer is a instrument which is used for separating the
components of light, which have different wavelengths. The
spectrum appears in a series of line called line spectrum
 This line spectrum is also called the Atomic Spectrum because it
originates in the element. Each element has a different atomic
spectrum.The production of line spectra by the atoms of an
element, indicates that an atom can radiate only certain amount of
energy. This leads to the conclusion that electrons cannot have
any amount of energy but only a certain amount of energy.
 The emission spectrum characteristics of some elements are
plainly visible to the naked eye when these elements are heated.
For example, when platinum wire is dipped into a strontium nitrate
solution and then inserted into a flame, the strontium atoms emit a
red color. Similarly, when copper is inserted into a flame, the flame
becomes green. These definite characteristics allow elements to
be identified by their atomic emission spectrum. Not all lights
emitted by the spectrum are viewable to the naked eye, it also
includes ultra violet rays and infra red lighting.
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The fact that only certain colors appear in an element's atomic emission
spectrum means that only certain frequencies of light are emitted. Each of
these frequencies are related to energy by the formula:
herein E is energy, h is Planck's constant and ν is the frequency. This
concludes that only photons having certain energies are emitted by the
atom. The principle of the atomic emission spectrum explains the varied
colors in neon signs, as well as chemical flame test results mentioned
above. Each of these frequencies are related to energy by the formula:
.
The frequencies of light that an atom can emit are dependent on states
the electrons can be in. When excited, an electron moves to a higher
energy level/orbital. When the electron falls back to its ground level the
light is emitted.
An emission spectrum is always the inverse of its absorption spectrum.
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Emission spectrum of
Hydrogen
 An emission spectrum is always the
inverse of its absorption spectrum.
 Emission spectrum of Hydrogen