Structure of Atom III Flashcards
what is an emission spectrum
The spectrum of radiation emitted by a
substance that has absorbed energy is called
an emission spectrum. Atoms, molecules or
ions that have absorbed radiation are said to
be “excited”. To produce an emission
spectrum, energy is supplied to a sample by
heating it or irradiating it and the wavelength
(or frequency) of the radiation emitted, as the
sample gives up the absorbed energy, is
recorded.
- the emission spectrum is a characteristic spectrum of each element
what is absroption spectrum
-photographic negative of emission spectrum
- when white light is from any source is passed through the solution or vapours of a sample substance and then analysed is called the spectroscope.
- when white light is passed,certain wavelengths are absorbed and othe others are given out in the spectrum. The colours which are absorbed are the same colours which are given out in the emission spectrum whihc is charcateristic for each atom/
what is spectroscopy and atomic spectrum
The study of emission or absorption
spectra is referred to as spectroscopy.
The emission spectra of atoms
in the gas phase, on the other hand, do not
show a continuous spread of wavelength from
red to violet, rather they emit light only at
specific wavelengths with dark spaces
between them. Such spectra are called line
spectra or atomic spectra
why are line emission spectra extremely important
-> each emission spectrum is unique to each element
-> the line spectrum can be used to identify the element
-> first discovered by robert bunsen
->Elements like rubidium (Rb), caesium (Cs)
thallium (Tl), indium (In), gallium (Ga) and
scandium (Sc) were discovered when their
minerals were analysed by spectroscopic
methods. The element helium (He) was
discovered in the sun by spectroscopic
method
difference b/w emision and absorptionspectum
absorption
(i)white light is passed through substance and few wavelengths are absorbed and rest all are given
(ii) consits of dark lines in an otherwise continous spectrum
(iii) always discontinuous
emission
(i) light/ radiation of the substance itself is passed through prism
(ii) consists of bright lines with dark spaces
(iii) may be continouosu or discontinuous
why are there many lines in the atomic spectrum
Any
sample of reasonable size contains an enormous number of atoms. Although a single atom can be in only
one excited state at a time, the collection of atoms contains all possible excited states. The light emitted as
these atoms fall to lower energy states is responsible for the spectrum
what are the 5 lines in hydroegn spectrum called
the first line is called H-alpha, send H-beta, H - gamma and H delta respectively
what are the colours of the lines in balmer series
(i) Red
green
blue
violet-1
violet-2
what does intensity of spectral lines depend upon
The brightness or
intensity of spectral lines depends upon the
number of photons of same wavelength or
frequency absorbed or emitted.
what is the important 5 types of spectralline in hydrogen spectrum
Lyman series
n1=1
n2=2,3,4…
UV
Balmer
n1=2
n2=3,4,5..
Visible
Paschen
n1=3
n2=4,5,6…
IR
Brackett
n1=4
n2=5,6,..
IR
Pfund
n1=5
n2=6,7..
IR
HUmphrey
n1=6
n2=7,8,…
IR
what is limting line
last line
n2= infinity
which of the line spectra of hydrogen has
i)highest energy and least wavelength
ii) least energy and highest wavelength
i) last line/limiting line/ marginal line
n2= infinity
ii) first line/starting line/initial line
n2=1
define
(i) ionization energy/ionization potential
(ii) separation energy
(iii)excitaton energy
Minimum amount of energy required to liberate an electron from the ground state of an
isolated atom is called the ionization energy.
n1=1; n2=infinitiy
Minimum energy required to remove an electron from its excited state is called as separation
energy.
n1 = 2, 3, 4, 5, …. n2
= infinity
Amount of energy required to shift an electron from ground state to any excited state.
Note : All these kinds of energy are always positive.
n1
= 1
n2 = 2, 3, 4, 5, ……
