Atomic Structure Questions and Answers

B 517 nm C 1010 nm D 205 nm The thereshold frequency vo for a metal for a metal is 7 0 x 10 4 s Calculate the kinetic energy of an elee emitted when radiation of frequency v 1 0 x 10 5 s 1 hits the metal

I will be taking an question to help you know what is my d oubt Let the example be A electron makes transition from 7th energy state to 2nd s tate Find number of spectral lines visible in Balmer series So here if I apply the formula An An 1 2 where An n 2 n1 then I am getting wrong answer So is there any diffe rent formula

A 3 33 B 4 33 K The packing fraction in the CsCl structure with anion anion contact along with anion cation contact will be CS CI TC TC A 11 3 1 B 11 3 1 1 c 2 1 D 2 1

2 15 points Calculate the probability that an electron described by a hydrogen atomic 1s wave function will be found within a 34 ao of the nucleu 5 within 1 5 as of the nucleus and c between 3 and 4 ao of the nucleus The walue of an is 5 291 x 10 1 meters the Bohr radius

C most part of the atom is empty space D alpha particles move with high speed For a wave frequency is 10 Hz and wavelength is 2 5 m How much distance it will travel in 40 secon

A 10 sec He B 20 sec 0 C 25 sec CO D 55 sec CO The ionization energy of the ground state hydrogen atom is 2 18x10 18 J The energy of an electro second orbit of He will be A 1 09x10 8 J B 4 36x10 J C 2 18x10 8 J D 2 18x10 8 J

How long would it take a radio wave of frequency 6 10 sec to travel from mars to the earth a distance of 8 x 107 km Rutherfords experiment which established the nuclear model of atom used a heam of

What is the advantage of squaring the wave function and then plotting against distance from the nucleus 1 Function becomes continuous 2 All the values becomes positive 3 Wave function stops showing two solutions at a point 4 The value 4 at r 0 becomes zero

Rutherfords experiment which established the nuclear model of atom used a beam of A B particles which impinged on a metal foil and get absorbed B y rays which impinged on a metal foil and ejected electron C Helium atoms which impinged on a metal foil and got scattered D Helium nuclie which impinged on a metal foil and got scattered

Atomic radius is of the order of 10 8 cm and nuclear radius is of the order of 10 13 cm Calculate what fraction of atom is occupied by nucleus With what velocity should an a particles travel towards the nucleus of a Cu atom co 12

A 600 W mercury lamp emits monochromatic radiation of wavelength 331 3 nm How many photons are emitted from the lamp per second h 6 6260 10 34 Js velocity of light 3 10 ms A 1 10 9 C 1 10 B 1 1020 D 1 1023 A A

1 Discusss the similarities and differences between a Is and a 2s orbital 2 Which quantum number tends to specify the orientation in space for an orbital 3 Which is the first energy level containing f orbitals 4 What is the relationship between wavelength and the momentum of a particle 5 What is the physical significance y of y and 5 What are degenerate orbitals

How to memorize this When we are asked to write electronic configuration of big ger elements what can be done to solve the question wit hin a minute Following is the increasing order of the energy of the orbit 18 25 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4 5d 6p 7s This order can be easily remembered in the following way 19 35 45 58 68 20 3P Ap SP op 3d 4d 54 6d Af 5f

2 42 In the Bohr s model for unielectronic species following symbols are used Radius of nth orbit with atomic number z Potential energy of electron in nth orbit with atomic number z Kinetic energy of electron in nth orbit with atomic number z Velocity of electron in nth orbit with atomic number z Time period of revolution of electron in nth orbit with atomic number z Calculate z in all cases 1 1 z U 2 K 2 8 1 iii V1 2 V3 1 9 1 Inz U 11 z K n Z V z T n z 1 212 1 1 8 T1 2 T2 2 9 32 Represent your answer as abcd where a b c and d represent number from 0 to 9 a b cc represents the value of z in parts i ii iii iv Suppose your answer is 1 2 3 4 th same must be filled in OMR sheet as1234 00

max According to photoelectric equation K hv The photoelectric emission will not be possible if I K is negative II max III K is positive max a I and II c III and II Vo IV Vo V b d V I and IV III and IV

ao IIT Academy What should be the ratio of the radii of the second orbit of Li 2 ion and the third orbit of Bet ion 0 B 16 27 C 4 9 D None of these A 3 1 The ratio of velocities of the electrons in the fifth orbit of Lit2 and He should be

The electron in a hydrogen atom makes a transition from an excited state to the ground state Which of the following statements is correct Its kinetic energy increases and its potential and total energies decrease Its kinetic energy decreases potential energy increases and its total energy remain A B a D constant Its kinetic and total energies decrease and its potential energy increases Its kinetic potential and total energies decrease

3 A gas is found to contain 2 34 g of nitrogen and 5 34 g of oxygen Simplest formula of the compound is 1 N O 3 N O 2 NO 4 NO

Which of the following statements about Avogadro s law is correct A At constant temperature and pressure equal volumes of all gases contain same number of molecules B The number of molecules in one litre of hydrogen is less than the number of molecules in one litre oxygen at constant temperature and pressure D It did not differentiate between atoms and molecules At constant temperature and pressure different volumes of all gases contain same number of molecules

Which one of the following was concluded from Rutherford s alpha particle scattering experiment A Electrons have negative charge B Most of the space in atom is empty Neutron exists in the nucleus D Alpha particles are four times as heavy as a hydrogen atom

The ionization energy of He is 19 6 10 18 J per atom Phe energy of the second stationary state in Li2 ion will be 214 4 9 10 18 44 1 x 10 18 J A C TITL B D 2 18 10 18 J 11 025 x 10 8 J

The correct statement on the aufbau principle is that n 1 d subshell is always lower in energy than ns orbital B n 1 f subshell is always has energy more than np orbital 5d is lower in energy than 4f X 6p is lower in energy than 5d C D 4

3 5 44 x 10 19 Cal 4 5 44 x 10 19 erg 0 5 g particle has 2 x 10 m uncertainity in position find the uncertainty in its velocity m s 1 3 0 x 1033 2 5 x 10 27 3 4 x 10 30 4 4 x 10 10

6 626 x 10 Js The expression of radius of a Bohr orbit in a hydrogen like species is 4n m Ze 4neo h A C 2 r n r n h 4n m Ze 4 E B D r 1 An m Ze Are h An m Ze 4

53 The overall formation constant for the reaction of 6 mol of CN with Cobalt II is 1 x 10 9 The formation constant for the reaction of 6 mol of CN with Cobalt III is X1063 Given that 019 Co CN 3 e Co CN 6 ERP 0 83 V Co 3 e 1 Co 2

State Heisenberg s uncertainty principle Calculate the uncertainity in the position of an electron in its velocity is i 0 001 ii zero Given velocity of electron 300m s State Afhau s principle 3

Which of the following staternents regarding Bohr theory of hydrogen atom is not correct A The ionization energy of atom is equal to the energy equivalent to Rydberg constant Speed of electron in the n 2 orbit is larger than that in the n 1 orbit Radius of orbit is directly proportional to square of quantum number n The distance between successive orbits increases with increase in the value of quantum number n B C D

Knowing precisely all the components of a non zero angular momentum of the electron in a hydrogen atom would violate Heisenberg s uncertainty principle The radial probability distribution function P r is maximum at r ao for the ground state of hydrogen atom however y attains maximum value at a different value of T 5 s orbital has angular independence i e for s orbital wave function is independent of and 8 9 AV BY D In the radial probability distribution function plots if n is the number of times the wave function changing its sign then number of radial nodes for that orbital is n 1

Here N is the number of electrons having parallel spins As the number of parallel spins increases the exchange energy also increases The exchange means the shifting of electrons from one orbital to another in the same sub shell This can be easily illustrated by considering chromium as example If the configuration is 3d 4s N is taken as 5 and C pairs of electrons equal to 10 is possible The exchange energy is 10K If the configuration is 3d5 4s N is taken as 6 and C pairs of electrons equal to 15 is possible The exchange is 15K

Which of the following statement s is are correct for a decay a when there is imblanace of number of neutrons and protons for stability a B particle is emitt b when the number of protons is more than that required for stability decay occurs c in a B deay a proton becomes a neutron at the expense of the binding energy of the parent nucleus releasing a positron and neutrino d when a nucleus undergoes B decay the total nucleon number remains constant

Given for H atom 1 1 9 3 a R r where 3 2 2Zr nao Orbital is 3s 4xr R r 6 60 0 e 0 2 Select the correct statement s for the given orbital a 0 53A Graph for the given orbital is n r Distance between radial nodes is equal to ao

1 Calculate the uncertanity in position assuming that the uncertainity in determining the momentum is 0 1 for an electron moving in an atom with a velocity of 2 2x10 ms 2 Expand A C and state under what condition A C A C 4 2

What possibly can be the ratio of the de Broglie wavelengths for two electrons each having zero initial energy and accelerated through 50 volts and 200 volts A 3 10 C 1 2 B 10 3 D 2 1

A particle X moving with a certain velocit has a de Broglie wavelength of 1 A I particle Y has a mass of 25 that of X and velocity 75 that of X de Brogli wavelength of Y will be A 3 C 6 88 B 5 33 D 48

The figure below is the plot of potential energy versus inter nuclear distance d of H molecule in the electronic ground state What is the value of net potential energy E as indicated in figure in KJ mol for d d at which the electron electron repulsion and the nucleus nucleus repulsion energies are absent As reference potential energy of H atom is taken as ZERO when its electron and nucleus are infinitely far apart NA 6 023 x 102 mol lith Eo Potential Energy k mol d H do Internuclear distance d

Q 33 Calculate the ground state energies of the 2 electron in eV in the case of He and Li RH 13 6 eV 1 13 60 eV and 54 40 eV 2 54 40 eV and 13 60 eV 3 54 40 eV and 122 40 eV vom 4 13 60 eV and 122 40 eV

or Ax Ap Ax Av mass X h 4 iiFor other canonical conjugates of motion the equation for Heisenberg uncertainty principle can be modified Momentum mass x velocity h m x 4 velocity time AE X At 2 force x time Momentum x distance force x distance x time energy x time x time Apx Ax AE x At h 4 T iii Why an electron cannot For energy and time exist in the nucleus The 10 14 to 10 15 m Hence if photon of light stril seen with the help displayed in Fig 2 the impact changes According to which the position the wavelength of It shows that shor position But a ra energetic in natur electron the im direction of the electron changes Photons with lon less effect on th larger waveleng position of the e

3 3 K Rb Cs K E 4 Cs Rb K K E Maximum electron in 3rd shell having m 2 will be 1 2 2 O 3 12 4 24 What about degeneracy of 2p orbitals in a magnetic field 1 No degenerate orbital 2 Three degenerate orbital 3 Two degenerate orbital 4 Cannot be stated any thing about degenracy 9 10

c In the case of bigger particles having considerable mass the value of uncertainty product is negligible Uncertainty principle is important only in the case of smaller moving particles like electrons For an electron of mass m 9 1 x 10 2 g the product of uncertainty is quite large Ax Av h 4 m 6 626 10 27 X 28 4 x 3 14 x 9 1 x 107 0 57 erg sec per gram approximately Note i For solving mathematical problems the expression of uncertainty principle is generally written as h Ax Ap 4 Incident Fig 2 26 Chang momentum an photon of light strike seen with the help of displayed in Fig 2 2 the impact changes i

tron be accelerated with a y may be given as charge on the particle lomb On vii we get vii with the help of de Broglie concept of wave nature of electron Consider an electron moving in a circular orbit around nucleus The wave train would be associated with the circular orbit as shown in Fig 2 23 If the two ends of the electron wave meet to give a regular series of crests and troughs the electron wave is said to be in phase i e the circumference of Bohrs orbit is equal to whole number multiple of the wavelength of the electron wave So 7 28 10 10 m or 10 39 m be measured as it waves but the Thus mation the following is its de Broglie ller is its de Broglie s independent of the sendent of charge From de Broglie equation or cable to microscopic en partiell molecule etc and has e wavelength is too which is difficult to oving electron and a travelling with the i e 2tr n N h mu 2tr 11 Wave in phase Z h mur n MU 2tr n Angular momentum n h 2 v velocity of electron and r radii of the orbit h 2 t 9 N Wave out of phase experiment confirm that When an zinc s with produced scintillation striking like a the our 2 21 Evidence to Support Particle and Wave Nature of Electron ii w was prove a D subjected filament the elect nickel ca Fig 2 23 This proves that the de Broglie and Bohr concepts are in perfect agreement with each other Note The calculations show that the velocity of de Broglie waves associated with a moving particle is greater than the velocity with which the particle moves Therefore it was difficult to understand as to how the de Broglie waves are associated with a particle A plausible solution to this problem is that a moving particle is associated with a wave packet rather than a wave Sou alec

4 The wavelength of second Balmer line in Hydrogen spectrum is 600 nm The wavelength for its third line in Lyman series is a 800 nm c 400 nm 016 b 120 nm d 200 nm WB JEE

24 The mass of beryllium 9 is 9 012182 g mol The mass of a proton is 1 007825 g mol The mass of a neutron is 1 008665 g mol Calculate the binding energy of Be 9 c 3 00 x 108 m s a 2 93 x 10 J mol b 8 12 x 10 1 J mol c 3 08 x 10 2 J mol d 5 54 x 10 2 J mol e 5 62 x 10 2 J mol

Consider the given table Metals Threshold frequency x10 s A 5 2 B 3 8 C 4 6 D 5 8 Photoelectrons ejected from which metal surface will have highest kinetic energy on irradiating with light of frequency 8 6 x 10 5 s O C OB O A

Calculate the internal energy and enthalpy changes resulting if air changes from an initial state of 5 C and 10bar where its molar volume is 2 312 x10 m mol to a final state of 60 C and 1 bar Assume also that air remains a gas for which PV T is constant and that C 20 785 and C 29 100 Jmol K

ii For gas molecules h mX Vrms where k Boltzmann h 3mkT constant 2 c In SS th certain ving 9 1

Calculate the maximum kinetic energy of photoelectrons emitted when a light the frequency 2 x 10 6 Hz irradiated on a metal surface with threshold frequency v equal to 8 68 10 5 Hz A 7 5 x 10 18 J C 2 9 x 10 4 J B 4 2 x 10 J D 10 6 x 104 J

If and are respectively the wavelengths of the series limit of Lyman and Balmer series of Hydrogen atom then the wavelength of the first line of the Lyman series of the H atom is 1 2 2 2 ydz 3 2 2 2122 2122 4 22 M

Due to inter electronic repulsion an electron experiences less nuclear charge It is therefore said that inner shell electrons shield the nucleus The actual nuclear charge experienced by an electron is called effective nuclear charge If the electrons in K shell shields the nucleus to the extent of 0 5 say each What will be the wave number of the spectral line arising out of n 4 to n 2 transition in Li atom A C 3 4 RH RH 4 3 B RH 8 D 8RH

29 a For an element with atomic number 29 i Write the electronic configuration ii Write the value of n and I for its electron in its valence shell b Name the set of d orbitals having the electron density along the axis

In context with the transition elements which of the following statements is incorrect In the highest oxidation states the transition metals show basic character and form cationic complexes In the highest oxidation states of the first five transition elements Sc to Mn all the 4s and 3d electrons are used for bonding Once the configuration is exceeded O the tendency to involve all the 3d electrons in bonding decreases In addition to the normal oxidation states the zero oxidation state is also shown by these elements in complexes