Atomic Structure Questions and Answers

4 It is equal to the mass of 1 mol of element in amu If the atomic mass unit u were defined to be 50 one fifth of the mass of C 12 what would be the atomic weight of N in amu on new scale 1 33 6 2 5 83 3 11 67 4 2 80 4 afe 441 41 3 1 1 5 1 33 6 3 11 67 4 12 g Namu 2 5 83 4 2 80

18 A proton is fired from very far away towards a nucleus with charge Q 120 e where e is the electronic charge It makes a closest approach of 10 fm to the nucleus The de Broglie wavelength in units of Fm of the proton at its start is take the proton mass m 5 3 10 27 kg hle 4 2 x 10 15 Js C 1 9x 10 m F 1 Fm 10 15 m IIT JEE

83 Magnetic field at the centre at nucleus of the hydrogen like atoms atomic number Z due to the motion of electron in nth orbit is proportional to 1 n Z5 2 n 4 Z 3 Z 3 n 4 Z 5 n

A particle of mass as an electron 1 mg has the same wavelength moving with a velocity of 3 x 106 m s 1 The velocity of the particle is mass of electron 9 1 10 1 kg 1 2 7 x 10 21 m s 1 3 9 10 2 m s 1 X AIPMT Prelims 2008 2 2 7 x 10 18 m s 1 4 3 x 10 31 m s 1

When light of wavelength is incident oneg surface the kinetic energy of photoelectron is E To increase the KE of the electron to 2E the incident wavelength must be hch 1 EX hc 3 2 2 4 hc E hc KIN 2

The binding energy per nucleon for a deuteron and an a particle are x and x respectively The energy Q released in the reaction H H He Q S A 2 x x C 4 x x A A B 2 x x D 4 x x

Monochromatic light of wavelength 667 nm is produced by a helium neon laser The power emitted is 9 mW The number of photons arriving per sec On the average at a target irradiated by this beam AIPMT Prelims 2009 is 2 9 1015 4 9 1017 1 3 1016 3 3 1019

2 The electron in the hydrogen atom jumps from excited state n 4 to its ground state n 1 and photon thus emitted irradiate a photosensitive metal If work function of metal is 2 75 eV the stopping potential is estimated to be 1 4 V 3 10 V 2 2 V 4 5 V

The particle is moving in a spherical symmetric potential r ar Here w constant Express the average potential energy of the particle in terms of the aven kinetic energy Answer a U T d U 3 r 86 B C D

De excitation of a moving hydrogen atom Consider a hydrogen atom with its electron excited to nth state moving at speed v c It emits a photon in the direction of its motion and changes its state to a lower state m If atom is kept at rest then for the transition from n to m state a frequency vo is emitted find the frequency of emitted photon in case when atom is moving

De Exitation by Emitting Two Photons A hydrogen like atom of atomic number Z is in a higher excited state of quantum number n The excited atom can make a transition by emitting two photons of energies 10 2 eV and 17 eV respectively An atom in same excited state can make a transition to n 3 by successively emitting two photons of energies 4 25 eV and 5 95 eV respectively Calculate the values of n and z

Various Spectral Lines From a H Like Atom A gas of hydrogen like atoms has some atoms in lowest energy level A and some atoms in a particular energy level B and there are no atoms in any other energy levels The atoms of gas gets exited to higher energy levels by absorbing monochromatic light of photons of 2 7 eV Subsequently during de excitation these atoms emit radiations of only six different spectral lines in spectrum Some of these radiations are of 2 7 eV some have less and some have more than 2 7 eV Find the quantum number of energy level B and ionization energy of these atoms

A nucleus of mass number A initially at rest emits an alpha particle The de Broglie wavelength of the emitted alpha particle is 2 Immediately after the emission the de Broglie wavelength of the nucleus is

I CH 4 CH C CH and H I CH 40 The most stable carbocation is and H 1 CH3 CH CH3 2 CH3 CH CH CH3 3 CH3 CH CH CH CH3 4 CH3 CH CH CH CH3 3 CH 8 42 CH is an 41 The most stable carbanion is consgab b 1 CH3 CH 1 Electrophile no radical 2 CH CH 4 CH CH 2 Nucleophile 4 Ambiphiles

A diatomic molecule is made of two masses m and m2 which are separated by a distance r If we calculate its rotational energy by applying Bohr s rule of angular momentum quantization its energy will be given by n is an integer 1 2 3 4 m m n h 2m m r n h 2 m m r 2n h m m r m m n h 87 m1m r

In a sample of hydrogen atom all electron are in a particular excited state n when all electrons return to ground state photon with six different wavelength are emitted Which of the following is are incorrect A Out of six different photon only 2 photons have speed equal to that of visible light B If highest energy photon emitted from the above sample is incident on the metal plate having work function 8 eV KE of liberated photo electron may be equal to or less than 4 75 eV C Total number of radial nodes in all the orbital of nth shell are 6 D Total number of angular nodes in all orbital of the n 1 th shell are 3

8 A drop of water has 550 excess electrons To keep it hanging in the air an electric field of 100 N C acting in vertically downward direction has to be applied The radius of the drop is about 1 6x 10 4 mm 3x10 4 mm 2 4 3 8x10 4 mm 1 10 4 mm 3

That when the elctrons release potential energy what actually happens is that they come to a low energy state and come close to the nucleus which directly affects the attractive force btw nucleus and electron and which is the cause for kinetic energy

Suppose the potential energy between a proton and an ke electron is given by U ke where r is the separation between the two Then the radius of the nth Bohr s orbit is proportional to Only one correct answer A n B 1 12 C n D 1 MA

1 Highly energetic electrons are bombarded on a target of an element containing 30 neutrons The ratio of radii of nucleus to that of Helium nucleus is 14 3 The atomic number of nucleus will be fach i saci 1 25 2 26 1 3 3 56 4 30 well

PASSAGE The energy difference between first excited state and ground state of a given system is 1 96 eV The transition occurs between first excited state and ground state Given K 8 6 X 10 5 eV K or 1 38 X 10 power 23 J K Choose the correct options Marks 2 The ratio of poulation of excited versus ground state at 27 degree celsius is OPTIONS 0 326x10 31 0 56 10 31 1 1x10 33

er system is capable of lasing at several infrared wavelengths where the most prominent ngth is 3 1235 mm Given k 8 6x 10 5eV K or 1 38 X 10 power 23 J K Choose the correct options Marks 2 Which state is occupied by atoms under conditions of th OPTIONS excited state ground state metastable state

PASSAGE A laser system is capable of lasing at several infrared wavelengths where the most prominent vavelength is 3 1235 mm Given k 8 6x 10 5eV K or 1 38 X 10 power 23 J K Which state is occupied by atoms under conditions of therma OPTIONS excited state ground state metastable state

PASSAGE In Ruby laser total number of Cr3 ions is 3x10 power 19 The laser emits radiation of wavelength 6940 Choose the correct op The energy of one emitt OPTIONS 2 86x10 power 19 J 6 23x10 191

A laser system is capable of lasing at several infrared wavelengths where the most prominent wavelength is 3 1235 mm Given k 8 6x 10 5eV K or 1 38 x 10 power 23 J K Choose the correct options Marks The relative population of these states at 45 degree C OPTIONS 0 98 0 78 0 58

4 A deuteron of kinetic energy 50 keV is describing a circular orbit of radius 0 5 m in a plane perpendicular to the magnetic field B The kinetic energy of the proton that describes a circular orbit of same radius and inside same B is a 25 keV Le b 100 keV c 200 keV d 50 keV

ASSAGE te Ne laser produces light of wavelength 6328 Angstrom at room temperature Choose the correct options Marks 1 The energy difference between two energy levels emitting this radiation in joule OPTIONS 2 14 10 19 314x10 1911

The hyperfine splitting of the spectral lines of an atom is due to a the coupling between the spins of two or more electrons b the coupling between the spins and the orbital angular momenta of the electron c the coupling between the electron spins and the nuclear spin d the effect of external electromagnetic fields

Tyndall effect is observed when 1 Diameter of dispersed particles is not much smaller than the wavelength of light used ii The refractive indices of the dispersed phase and dispersion medium differ greatly in magnitude iii Diameter of dispersed particles is much larger than the wavelength of the light used 1 i and ii 2 i and iii 3 ii and iii 4 i ii and iii

A sample of hydrogen atoms de excites from 6th excited state to the ground state in one or more electronic transitions If no spectral line is obtained in the Paschen and Brackett series then the maximum number of spectral lines of different photon energies obtained will be Question Type Single Correct Type 1 21 2 15 2 10

A 01 24 An electron a proton an a particle and a hydrogen atom are moving with the same kinetic energy the associated de Broglie wavelength will be longest for B Proton C a particle A Electron 25 The radius of the 4th orbit of the electron will be smaller than its 8th orbit by a factor of A 2 B 4 C 8

162 3 The energies of three conservative energy levels L3 L and L of hydrogen atom are E respectively A photon of wavelength is emitted for a transition L to L What will be the wavelength c emission for transition L to L 31 19 20 2 4E0 9 27A 7 and Eo 4

Two radiations of photons energies 1 eV and 2 5 eV successively illuminate a photosensitive metallic surface of work function 0 5 eV The ratio of the maximum speeds of the emitted electrons is AIPMT Mains 2012 2 1 2 4 1 5 1 1 4 3 1 1

dissociate into atoms 4 Average lifetime of a hydrogen atom excited to n 2 state is 10 8 s Find the number of revolutions made by the electron on the average before it jumps to the ground state

An electron of mass m with an initial velocity V voi vo 0 enters an electric field E Ei E constant 0 at t 0 If is its de Broglie wavelength initially then its de Broglie wavelength at time t is NEET 2018 1 3 2 1 20 eEo t mvo 2 A 1 4 t eEo mvo

An electron is accelerated through a potential difference of 10 000 V Its de Broglie wavelength is nearly m 9 x 10 31 kg NEET 2019 1 12 2 x 10 13 m 3 12 2 10 14 m 2 12 2 x 10 12 m 4 12 2 nm

4 All of these For what distance is ray optics and approximation when a plane light wave is incident on a slit aperture of width 2mm having wavelength 600nm elegram n 1 6m 2 8m 3 6 7m 4 4m What is the approximate radius of the central bright 10

SolveLancer Test If mass of an electron in an atom of hydrogen increases by 50 then radius of its orbit change by what percent SolveLancer Test a Increases by 70 b Decreases by 50 c Increases by 50 d None of the above

A Bohr hydrogen atom undergoes a transition n 5 to n 4 and emits a photon of frequency f The frequency of circular motion of electron in n 4 orbit is f The ratio is found out to be 2p 25 Find the value of p h

In a P N junction diode not connected to any circuit 1 The potential is the same everywhere 2 The P type side is at higher potential than the N type side 3 There is an electric field at the junction directed from the P type side to the N type side 4 There is an electric field at the junction directed from the N type side to the P type side

Question No 8 Electrons are emitted from an electron gun at almost zero velocity and are accelerated by an electric field E through a distance of 1 0 m The electrons are now scattered by an atomic hydrogen sample in the ground state What should be the minimum value of E so that red light of wavelength 656 3 nm may be emitted by the hydrogen Options 3 4 Volt m 20 4 Volt m

A neutron beam of initial kinetic energy Eo is divided into two beams at point O by some mechanism Thereafter the beams proceed on the path OAC and OBC without a phase change at the corners A and B to interfere with each other at point C Here OACB is a square of side l tilted at an angle above the horizontal Mass of a neutron is m Planck s constant is h and acceleration of free fall is g Find an expression for the angle at which a maxima is detected at point C

A hydrogen like atom atomic number Z is in a higher excited state of quantum number n This excited atom can make a transition to the first excited state by successively emitting two photons of energies 10 20 eV and 17 00 eV respectively Alternatively the atom from the same excited state can make a transition to the second excited state by successively emitting two photons of energies 4 25 eV and 5 95 eV respectively Determine the value of Z Ionization energy of hydrogen atom is 13 6 eV O 1 2 3 Insufficient data

33 An electron is accelerated from rest between two points A and B at which the potentials are 20V and 40 V respectively The De Broglie wavelength associated with the electron at B will be 1 0 75 2 7 5 3 2 75 4 2 75 m

Q 6 The de Broglie wavelength of an electron emitted from the ground state of an H atom after the absorption of a photon equals of the de Broglie wavelength when it was in orbit The energy of the photon absorbed is Answer A B Your Attempt 68eV 13 6eV Correct answer Rate this quest

The electrostatic energy of a nucleus of charge Ze is where k is a constant and Ris the kZ e equal to R nuclear radius The nucleus divides into two daughter nuclei of charges and equal radii The Ze 2 change in electrostatic energy in the process when they are far apart is

A spectral line results from the transition n 2 ton 1 in the single electron system given below Which one of these will produce the shortest wavelength emission 1 H 2 Het 3 Litt 4 Ducterium atom

The electron in a hydrogen atom makes a transition from a lower energy state to a higher energy state by absorbing a photon of energy 2 55 eV If the radius of the orbit which the electron was initially occupying was r the radius of its final orbit is A 2r B 4r C 16 9 r D 9 4 r

An electromagnetic wave of intensity 30 W m is incident on a surface of area 2 m If the surface is perfectly absorbing then the amount of momentum transferred to the surface in 10 s will be O 2x 10 6 kg m s 0 2 x 106 kg m s O 4 x 10 9 kg m s 010 8 kg m s

The mass based ratio of U238 and Pb226 in sample of rock is 4 3 If half life of U238 4 5 x 10 yr then age of the rock is 6x103 1 6 3 10 yr 3 38 10 vr 2 4 5 x 109 yr 4 6 2 x 109 yr J