Atomic Structure Questions and Answers

PHOTO ELECTRIC EFFECT The frequency of a photon associated with an energy of 3 31 eV is given h 6 62 x 10 34 Js 1 0 8 x 10 5 Hz 2 1 6 x 10 5 Hz 3 3 2 x 10 5 Hz 4 8 0 x 10 5 Hz A radiation of wave length 2500 A is incider on a metal plate whose work function is 3 V Thor the otential required to stop t

84 A metal plate of area 1x10m is illuminated by a radiation of intensity 16mW m The work function of the metal is 5eV The energy of the incident photons is 10eV and only 10 of it produces photo electrons The number of emitted photo electrons per second and their maximum energy respectively will be leV 1 6x10 J JEE 2018 a 10 and 5eV b 10 4 and 10 eV c 10 and 5 eV d 10 and 5 eV

25 A parallel beam of electrons travelling in x direction falls on a slit of width d see figure If after passing the slit an electron acquires momentum p in the y direction then for a majority of electrons passing through the slit h is Planck s constant 1 pd h Y X

If the edge length of a NaH unit cell is 488 pm what is the length of Na H bond if it crystallises in the fo structure 1 122 pm 2 244 pm 3 488 pm 4 974 pm

3 A proton is accelerated through 225 V Its de Broglie wavelength is 1 0 1 nm 2 0 2 nm 3 0 3 nm 4 0 4 nm 1 h V2 m qv Regd Office Aak

The absorption transition between the first and the fourth energy states of hydrogen atom are 3 The emission transition between these states will be

5 A single electron orbits around a stationary nucleus If 47 2 eV is required to excite the electron from the second orbit to third orbit Assume the model is Bohr s atomic model Then mark the correct options A Number of protons in the nucleus is five b Total energy of electron is in ground state 340 eV Kinetic energy of electron in ground state is 340 eV d Potential energy of electron in ground state is 680 eV

20 The distance of closest approach of an alpha particle with velocity V approaching a gold nucleus is d Then the distance of closest approach when the velocity becomes 2V is 1 D 2 d 2 2 od 01 4

d Excess of electrons over protons in a body is responsible for positive charge of the body 9 Charge on a body which carries 200 excess electrons is a 3 2 x 10 18 C b 3 2 x 10 18 C c 3 2 x 10 17 C d 3 2 x 10 17 C

7 In Latt electron in first Bohr orbit is excited to a level by a radiation of wavelength 2 When the ion gets de excited to the ground state in all possible ways including intermediate emissions a total of six spectral lines are observed What is the value of Take h 6 63 x 10 34 Js c 3x108 ms 1 44 111 tv

Find the ratio of de Broglie wavelength of proton and a particle which have been accelerated through same potential difference 1 2 2 3 5 3 2 3 7 4 13 2

The ratio of wavelength of an electron revolving in 3rd orbit to that of revolving in 5th orbit in H atom is 1 2 5 2 5 3 3 2 3 4 3 5

m If the momentum of an electron is changed by then the de Broglie wavelength associated with it changes by 0 50 The initial momentum of electron will be 1 400P 3 200 s 42 200P 4 16 Pm 400 m

Avalanche breakdown in a PN junction due to 1 Sudden shift to Fermi level 2 Increase in the width of forbidden gap 3 Sudden increase of impurity concentration 4 Cumulative effect of increased electron collision and creation of added electron hole pairs

35 The ratio of the speed of the electron in the ground state of hydrogen to the speed of light in vacuum is 1 1 3 1 2 1 137 2x 2 4 2 237 2 137 2 300

The radius of the first permitted Bohr orbit for the electron in a hydrogen atom equals 0 51 A and its ground state energy equals 13 6 eV If the electron in the hydrogen atom is replaced by muon u charge same as electron and mass 207 m the first Bohr radius and ground state energy will be NEET 2019 Odisha 1 2 56 x 10 13 m 13 6 eV X 2 0 53 10 13 m 3 6 eV 3 25 6 x 10 13 m 2 8 eV 1

Two identical non relativistic particles A and B move at right angles to each other processing de Broglie wavelength and respectively The de Broglie wavelength of each particle in their centre of mass frame of reference is A 2 2 C 2 2 2 1 B 22 2 2 2 D 2 2 2

The quantum numbers 1 2 and 1 2 for the electron spin represent 1 Rotation of the electron in clockwise and an ticlockwise direction respectively 2 Rotation of the electron in anticlockwise and clockwise direction respectively 3 Magnetic moment of the electron pointing up and down respectively 4 Two quantum mechanical spin states which have no classical analogue

4 A coin is made up of Al and weighs 0 75 g It has a square shape and its diagonal measures 17 mm It is electrically neutral and contains equal amount of positive and negative charges The magnitude c these charges is Atomic mass of Al 26 98 g a 3 47 x 104 C c 1 67 x 1020 C b 3 47 x 102 C d 1 67 x 1022 C

Which of the following equilibrium shifts in backward direction by applying high pressure 2NO g N O g 2 H g Cl g 3 PCI g Cl g 2HCl g PCI g N g 3H g 2NH g

Which of the following reactions represents a fission reaction O 22H He n O 235U In 14 Ba 32 Kr 3 n 92 56 36 0 150 5N e OH He je

to 3 If one were to apply Bohr mod particle of mass m and charge q moving in a plane under the influence of a magnetic field B the energy of the charged particle in the nth level will be 1 n hqB 2 m 2 n hqB 4 m hap

During revolution around an atomic nucleus an elec tron transits from one orbit to another The radius of the present orbit is 4 times that of the former orbit while the linear velocity is reduced to half of its initial value Determine the ratio of its angular momentum in the two orbits 1 2

Which of the following statements is incorrect A B Probabilities are found by solving Schrodinger wave equation Energy of the electron in an atom at infinite

A photon of 10 2 eV energy collides with a hydrogen atom in ground state inelastically After fe microseconds one more photon of energy 15 eV collides with the same hydrogen atom Then wh can be detected by a suitable detector JEE 2005 Scr A one photon of 10 2 eV and an electron of energy 1 4 eV B 2 photons of energy 10 2 eV C 2 photons of energy 3 4 eV D 1 photon of 3 4 eV and one electron of 1 4 eV

33 Output is LOW if and only if all the inputs are HIGH Indicate the logic gate for which the above state ment in ture 1 AND 2 OR 3 NOR 4 NAND

Rutherford s experiment established that A Inside the atom there is a heavy positive centre B Nucleus contains protons and neutrons C Most of the space in the atoms is empty D Size of the nucleus is very small

77 If the P E of a Bohr s hydrogen atom in the ground sta is zero then its total energy in the first excited state w be a 13 6 eV al 119 c 10 2 eV b 27 2 eV d 23 8 eV 13 6

3 The light of wavelength 4000 falls on a photosensitiv substance whose work function is 2 eV Its stoppin potential is a 1 1 V c 1 26 V b 1 8 V d 0 8 V AIIMS

6 Out of the following which one is not a possible energy for a photon to be emitted by hydrogen atom according to Bohr s atomic model AIPMT Mains 2011 1 13 6 eV 2 0 65 eV

1800 A Si specimen is doped with Al The concentration of acceptor atoms is 1021 atom m3 If concentration of electrons in the specimen is 1017 m3 the intrinsic concentration of electron hole pair is 4 18000 1 1014 m3 2 1017 m3 3 1019 m3 4 1021 m3 The cut off wavelength for photoelectric effect is

An electron beam has a kinetic energy equal to 100 eV The wavelength associated with the beam is approximately Given mass of electron 9 1 x 10 31 kg Planck s constant 6 6 10 34 Js and 1 eV 1 6 10 J a 0 12 h 1 28 s 128 d 129 8

Assume that the de Broglie wave associated with an electron can form a standing wave between the atoms arranged in a one dimensional array with nodes at each of the atomic sites It is found that one such standing wave is formed if the distance d between the atoms of the array is 2 A similar standing wave is again formed if d is increased to 2 5 but not for any intermediate value of d Find the energy of the electrons in eV A 302 eV B 151 eV C 75 5 eV D 75 5 106 eV The least value of d for which the standing wave of the type described above can form A 0 4 A B 0 5 A C 2 A

Two hydrogen atoms are in excited state with electrons residing in n 2 First one is moving towards left and emits a photon of energy E towards right Second one is moving towards left with same speed and emits a photon of energy E towards left Taking recoil of nucleus into account during emission process A E E E E arxas B E E D information insufficient

1 1 73 x 10 43 m 2 1 73 x 10 45 m 3 1 73 x 10 15 m 4 1 73 x 10 13 m In process of nuclear fission of 1 g uranium the mass lost is 0 90 mg The efficiency of power house s fission reactor is 20 To obtain 400 mega watt power from the power house how much uranium required per hour 1 88 g 3 44 g 2 178 g 4 22 g Initial numbe is 5 x 1016 nuclei dec 38 1 2 x 1 3 3 5 Bindin Find 1 C 3 39 A 39 H

Find the energies needed to remove a neutron from He then o remove a proton and finally to separate the remaining neutron and proton Compare the total with the binding energy of He

The energy of a photon a sodium light 589 nm equals the band gap of a semi conducting material Find the v of 300 K of E kT at a temperature

6 Which scientist defined the areas of probability of where electrons can be found orbiting the nucleus of an atom Rutherford Bohr O Shr dinger Thomson

2 The energy levels for a Bohr atom are shown below O 117 5 eV O 114 8 eV 4 90 eV 7 65 eV 13 6 eV 108 8 eV 30 6 eV What amount of energy is needed for an electron to jump from n 1 to n 3 h 6 626 x 10 34 1 eV 1 6 x 10 1 J 122 4 eV n 5 n 4 n 3 n 2 n 1

Which one of these electron transitions involves the smallest amount of energy change A D OB OC OD O A B C

A neutral object can become positively charged by Select one a losing electrons b gaining protons c losing protons O d gaining electrons

3 Complete the table below For example in the first row decide whether Sc is a cation or anion In the second row writ the symbol for the ion that an atom of calcium is mostly likely to form and then decide what type of ion it is S element scandium calcium iodine rubidium oxygen symbol of ion 3 Sc most likely ion U type of ion cation cation cation cation cation anion anion anion anion anion X 5

Objects ordinarily have equal numbers of electrons and protons and are therefore electrically Select one O a negative O b positive O C neutral

na neutral atom there are as many as protons

What are properties of a gamma ray Choose all that apply increases the atomic number by 1 decreases the atomic number by 2 has no affect on atomic number has no affect on atomic mass weakest form of radiation a helium nucleus is a form of electromagnetic energy strongest form of radiation an electron

Question Co is the element cobalt while CO is carbon monoxide Do you see a reason for clearly indicating lower case from upper case letters 3 Naming Acids

The laser light used to read a video disc has a wavelength of 405 nm 4 05 x 107 m This is in the violet part of the visible spectrum What is the frequency of this laser light

3 The energy needed to lonize a hydrogen atom in the ground state is Proof Explain 1 2 9 eV 2 3 2 eV 4 Photons incident upon hydrogen atoms in the n 2 level raise the energy of the atoms to the n 4 level What is the energy of the incident photons 1 1 89 eV 2 2 55 ev 3 13 06 eV 4 13 6 eV Proof Calculation 3 3 40 ev 4 4 25 ev 5 Several hydrogen atoms are supplied with sufficient energy to excite them to the n 3 energy level As the atoms return to the ground state how many different energy level transitions are possible 1 1 2 2 3 3 4 4 Proof Draw levels and arrows to show transitions 6 A photon with 15 5 electron volts of energy is incident upon a hydrogen atom in the ground state If the photon is absorbed by the atom it will 1 ionize the atom 2 excite the atom to n 2 3 excite the atom to n 3 4 excite the atom to n 4 7 An electron in the c level of a mercury atom is hit with a photon that has 6 62 electron volts of energy Which of the following will happen 1 The electron is moved to the ground state 2 The electron leaves the atom with a kinetic energy of 6 62 ev The electron leaves the atom with a kinetic energy of 1 10 eV The electron absorbs 5 52 eV of energy 3 4 Proof Calculation 8 What energy photon is needed for an electron in the n 5 level of a hydrogen atom to leave with a kinetic energy of 5 06 eV 1 0 54 eV 2 5 60 ev Proof Calculation Proof Explain 3 6 14 eV 4 13 6 eV 9 The bright line emission spectrum of an element can best be explained by 1 protons being dispersed uniformly throughout the atoms of that element 2 electrons being located in the nucleus 3 protons acting as both particles and waves 4 electrons transitioning between discrete energy levels in the atoms of that element

5 4 90 eV 7 65 eV 13 6 eV 4 30 6 eV ch of the following transitions would require the absorption of a photon Choose all that apply 122 4 eV n 5 n 4 n 3 n 2 n 1 PREVIOUS 4 of 10 NEXT

3 CI Based on the Lewis structure given the formal charge on the central chlorine atom is ww