Atomic Structure Questions and Answers

3 a Two stable isotopes of lithium Li and Li have respective abundances of 7 5 and 92 5 These isotopes have masses 6 01512 u and 7 01600 u respectively Find the atomic mass of lithium no 10 p 11 r

A Bohr hydrogen atom at rest in free space undergoes a transition from the energy level n 2 to n 1 emitting a photon in the positive x direction Since this photon has momentum the atom must recoil in the negative x direction Find the recoil velocity of the atom A 125 cm sec C 225 cm sec B 325 cm sec D 425 cm sec

An electron of mass m and charge e accelerated from rest through a potential difference Vin vacuum The fina speed of electron will be O O O lev 2e V m 02 56 hr min 12e V m

11 a By using the deBroglie relation derive the Bohr condition mur n for the angular momentum of an electron in a hydrogen atom b Use this expression to show that the allowed electron energy states in hydrogen atom can be written me En 88h n c How would this expression be modified for the case of a triply ionized beryllium atom Be Z 4 d Calculate the ionization energy in eV of Be 3 ionization energy of hydro gen 136eV

As per Pauling the radius of an a given crystal is inversely proportional to the effective nuclear charge Z Z Z 0 where o represents the screening constant The crystal structure of NaF is shown as below F Nat F Na X X F Nat Nat F 4 7 130 x The value o

c 3 2x10 8 eV d 3 3x10 8 eV 3 Find the energy of photon in watt hour for electromagnetic waves of wavelengths 3000 of wi Given h 6 6 10 34 Js b 2 1022 Wh d 1 83 1022 Wh a 2x10 22 Wh c 1 83 10 22 Wh

An electron of mass me has a speed un in the nth Bohr orbit of a hydrogen atom The normalized speed V is given as Vn un c 1 685 and the mass of the electron in the units of energy is given as Me mec 0 51 x 106 eV where e is the velocity of light in vacuum It is given that 2ehe 1 137 The Planck s constant h is given as 4 13 x 10 15 eV sec The electron makes a transition from nth orbit to the ground state of the atom What is the frequency of the emitted photon X1 3 29 x 10 5 Hz 2 3 16 x 1015 Hz X3 2 47 x 1015 Hz X 4 293 x 1015 Hz

4 A small mirror of area A and mass m is suspended in a vertical plane by means of a weightless string A beam of light of intensity I falls normally on the mirror and the string is deflected form the vertical through a very small angle a Assuming the mirror to be perfectly reflecting obtain an expression for a 21A I c mg c mg 31 c mg a C b d None of the above 21 C mg

A hydrogen atom at rest de excites from n 2 state to n 1 state if recoil of atom is not taken into account then the percentage error in momentum of photon is a x 10 7 The value of 5a is The energy equivalent of rest mass of hydrogen atom is 940 Mev

Three photons coming from excited atomic hydrogen sample are observed their energies are 12 1 eV 10 2 eV and 1 9 eV These photons must come from a Single atom c Three atoms b Two atoms d Either two or three atom TPHO As the electron in Bohr orbit of hydrogen atom passes from state n 2 to n 1 the kinetic

Bohr s atom model assumes a The nucleus is of infinite mass and is at rest b Electrons in a quantized orbit will not radiate energ c Mass of electron remains constant d All the above conditions

82 The diagram shows the path of four a particles of the same energy being scattered by the nucleus of an atom simultaneously Which of these are is not physically possible 1234 1 2 3 4 a Both 3 and 4 c Both 1 and 4 None of these b Both 2 and 3 d Only 4

2 A electron of mass m when accelerated through a potential difference V has de Broglie wavelength A The de Broglie wavelength associated with a proton of mass M accelerated through the same potential difference will be a m M b M C M m d 2 M m

The ratio between acceleration of the electron in singly ionised helium atom and doubly ionised lithium atom 1 both in ground state is a c 8 27 b d 27 8 Z

62 The velocity of an electron in the second orbit of sodium atom is v The velocity of an electron in its fifth orbit will be a v 5 C V 2 an ain b v 2 d v

3 Hydrogen atom emits blue light when it jumps from n 4 energy level to the n 2 level Which colour of light would the atom emit when it changes from the n 5 level to the n 2 level a Red b Yellow c Green d Violet