Chapter 2 - Structure of Atom

Calculate the energy and frequency of the radiation emitted when an electron
jumps from n = 3 to n = 2 in a hydrogen atom.

Assertion (A) : It is impossible to determine the exact position and exact
momentum of an electron simultaneously.
Reason (R) : The path of an electron in an atom is clearly defined.
(i) Both A and R are true and R is the correct explanation of A.
(ii) Both A and R are true and R is not the correct explanation of A.
(iii) A is true and R is false.
(iv) Both A and R are false.

Assertion (A) : Black body is an ideal body that emits and absorbs radiations
of all frequencies.
Reason (R) : The frequency of radiation emitted by a body goes from a lower
frequency to higher frequency with an increase in
temperature.
(i) Both A and R are true and R is the correct explanation of A.
(ii) Both A and R are true but R is not the explanation of A.
(iii) A is true and R is false.
(iv) Both A and R are false.

In the following questions a statement of Assertion (A) followed by a statement
of Reason (R) is given. Choose the correct option out of the choices given
below each question.

Assertion (A) : All isotopes of a given element show the same type of chemical
behaviour.
Reason (R) : The chemical properties of an atom are controlled by the
number of electrons in the atom.
(i) Both A and R are true and R is the correct explanation of A.
(ii) Both A and R are true but R is not the correct explanation of A.
(iii) A is true but R is false.
(iv) Both A and R are false.

Match the quantum numbers with the information provided by these.
Quantum number Information provided
(i) Principal quantum number (a) orientation of the orbital
(ii) Azimuthal quantum number (b) energy and size of orbital
(iii) Magnetic quantum number (c) spin of electron
(iv) Spin quantum number (d) shape of the orbital

Hydrogen atom has only one electron, so mutual repulsion between electrons
is absent. However, in multielectron atoms mutual repulsion between the
electrons is significant. How does this affect the energy of an electron in the
orbitals of the same principal quantum number in multielectron atoms?

Table-tennis ball has a mass 10 g and a speed of 90 m/s. If speed can be
measured within an accuracy of 4% what will be the uncertainty in speed
and position?

Out of electron and proton which one will have, a higher velocity to produce
matter waves of the same wavelength? Explain it.

What is the experimental evidence in support of the idea that electronic energies
in an atom are quantized?

According to de Broglie, matter should exhibit dual behaviour, that is both
particle and wave like properties. However, a cricket ball of mass 100 g does
not move like a wave when it is thrown by a bowler at a speed of 100 km/h.
Calculate the wavelength of the ball and explain why it does not show wave
nature.

Wavelengths of different radiations are given below :
λ(A) = 300 nm λ(B) = 300 μm λ (C) = 3 nm λ = 0 (D) 30 A
Arrange these radiations in the increasing order of their energies.

Wavelengths of different radiations are given below :
λ(A) = 300 nm λ(B) = 300 μm λ (C) = 3 nm λ = 0

An atom having atomic mass number 13 has 7 neutrons. What is the atomic
number of the atom?

Which of the following will not show deflection from the path on passing
through an electric field?
Proton, cathode rays, electron, neutron.

The arrangement of orbitals on the basis of energy is based upon their (n+l )
value. Lower the value of (n+l ), lower is the energy. For orbitals having same
values of (n+l ), the orbital with lower value of n will have lower energy.
I. Based upon the above information, arrange the following orbitals in the
increasing order of energy.
(a) 1s, 2s, 3s, 2p
(b) 4s, 3s, 3p, 4d
(c) 5p, 4d, 5d, 4f, 6s
(d) 5f, 6d, 7s, 7p
II. Based upon the above information, solve the questions given below :
(a) Which of the following orbitals has the lowest energy?
4d, 4f, 5s, 5p
(b) Which of the following orbitals has the highest energy?
5p, 5d, 5f, 6s, 6p

Calculate the total number of angular nodes and radial nodes present in 3p
orbital.

Nickel atom can lose two electrons to form Ni2+ ion. The atomic number of
nickel is 28. From which orbital will nickel lose two electrons.

Show the distribution of electrons in oxygen atom (atomic number 8) using
orbital diagram.

Write the electronic configuration of (i) Mn4+, (ii) Fe3+ (iii) Cr2+ and Zn2+
Mention the number of unpaired electrons in each case.

What designations are given to the orbitals having
(i) n = 2, l = 1 (ii) n = 2, l = 0 (iii) n = 4, l = 3
(iv) n = 4, l = 2 (v) n = 4, l = 1?

Arrange the electrons represented by the following sets of quantem number
in decreasing order of energy.
1. n = 4, l = 0, m = 0, s = +1/2
2. n = 3, l = 1, m = 1, s = -1/2
3. n = 3, l = 2, m = 0, s = +1/2
4. n = 3, l = 0, m = 0, s = -1/2

How many spherical nodal surfaces are there in 4s – sub-shell?

What is nodal surface or nodes?

Which quantum number determines
(i) energy of electron (ii) Orientation of orbitals.

Why is energy of 1s electron lower than 2s electron?

What is the meaning of quantization of energy?

Which orbital is non – directional?

What is the physical significance of y 2 up?

Calculate the uncertainty in the velocity of a wagon of mass 4000kg whose
position is known accurately of ±10m

Calculate the uncertainty in the momentum of an electron if it is confined to a
linear region of length 1´10-10.

Why cannot the motion of an electron around the nucleus be determined
accurately?

Give the de – Broglie’s relation.

We don not see a car moving as a wave on the road why?

How would the velocity be effected if the position is known?

Give the mathematical expression of uncertainty principle.

States Heisenberg’s Uncertainty Principle.

Spectral lines are regarded as the finger prints of the elements. Why?

What transition in the hydrogen spectrum would have the same
wavelength as the Balmer transition, n = 4 to n = 2 of He+ spectrum?

What is emission and absorption spectra?

Calculate energy of 2mole of photons of radiation whose frequency
is 5´1014Hz.

What is the relation between kinetic energy and frequency of the
photoelectrons?

What did Einstein explain about photoelectric effect?

Name the scientist who demonstrated photoelectric effect experiment.

What is threshold frequency?

How does the intensity of light effect photoelectrons?

Define photoelectric effect.

On what frequency does the frequency from a black body depend?

What did Planck’s theory explain?

Calculate the frequency and energy of a photon of radiation having
wavelength 3000
0A
.

Give the relation of energy (E) and frequency (v) as given by Planck.

Define quantum.

Define black body radiation.

Calculate the wavelength corresponding to a frequency of 98.8MHz.

What is an electromagnetic radiation?

State the two developments that led to the formation of Bohr’s model of atom.

Give the range of wavelength of the visible spectrum.

Why Rutherford’s model could not explain the stability of an atom?

What did Rutherford conclude from the observations of a - ray
scattering experiment?

Give the drawbacks of J.J. Thomson’s experiment.

Give the main features of Thomson’s Model for an atom.

Find out atomic number, mass number, number of electron and
neutron in an element 4 0
2 0 ´ ?

What is a mass number?

What is an atomic number?

What are isotones?

What are isobars?

What is an isotope? [

Name the scientist who first gave the atomic model.

Give the main properties of canal ray experiment.

Which experiment led to the discovery of electrons and how?

(i) What is the mass of a neutron? 
(ii) What is the charge of a neutron?

(i) What is the mass of a proton? 
(ii) What is the charge of a proton?

What is the mass (m) of an electron?

What is the charge (e) of an electron?

What is the e/m ratio of an electron?

Name the scientist who first formulated the atomic structure.

Name the sub – atomic particles of an atom.

(a) How many sub-shells are associated with n = 4? (b) How many electrons will be present in the sub-shells having m_s value of -1/2 for n = 4?

Indicate the number of unpaired electrons in: (a) P, (b) Si, (c) Cr, (d) Fe and (e) Kr.

The unpaired electrons in Al and Si are present in 3p orbital. Which electrons will experience more effective nuclear charge from the nucleus?

Among the following pairs of orbitals which orbital will experience the larger effective nuclear charge? (i) 2s and 3s, (ii) 4d and 4f, (iii) 3d and 3p

The bromine atom possesses 35 electrons. It contains 6 electrons in 2porbital, 6 electrons in 3porbital and 5 electrons in 4porbital. Which of these electron experiences the lowest effective nuclear charge?

The quantum numbers of six electrons are given below. Arrange them in order of increasing energies. If any of these combination(s) has/have the same energy lists:

1. n= 4, l = 2, ml= -2 , ms= -1/2

2. n= 3, l = 2, ml= 1 , ms= +1/2

3. n= 4, l = 1, ml= 0 , ms= +1/2

4. n = 3, l= 2, ml= -2 , ms= -1/2

5. n = 3, l= 1, ml= -1 , ms= +1/2

6. n = 4, l= 1, ml= 0 , ms= +1/2

If the position of the electron is measured within an accuracy of + 0.002 nm, calculate the uncertainty in the momentum of the electron. Suppose the momentum of the electron is h/4À_m x 0.05 nm, is there any problem in defining this value.

The velocity associated with a proton moving in a potential difference of 1000 V is 4.37 x 10⁵ms^-1. If the hockey ball of mass 0.1 kg is moving with this velocity, calculate the wavelength associated with this velocity.

If the velocity of the electron in Bohr's first orbit is 2.19 x 10⁶ms^-1, calculate the de Broglie wavelength associated with it.

Similar to electron diffraction, neutron diffraction microscope is also used for the determination of the structure of molecules. If the wavelength used here is 800 pm, calculate the characteristic velocity associated with the neutron.

Dual behaviour of matter proposed by de Broglie led to the discovery of electron microscope often used for the highly magnified images of biological molecules and other type of material. If the velocity of the electron in this microscope is 1.6 x 10⁶ms^-1, calculate de Broglie wavelength associated with this electron.

Calculate the wavelength for the emission transition if it starts from the orbit having radius 1.3225 nm and ends at 211.6 pm. Name the series to which this transition belongs and the region of the spectrum.

Emission transitions in the Paschen series end at orbit n= 3 and start from orbit n and can be represented as v = 3.29 x 10¹⁵(Hz) [1/3²- 1/n²]

Calculate the value of nif the transition is observed at 1285 nm. Find the region of the spectrum.

If the photon of the wavelength 150 pm strikes an atom and one of its inner bound electrons is ejected out with a velocity of 1.5 x 10⁷ms^-1, calculate the energy with which it is bound to the nucleus.

The ejection of the photoelectron from the silver metal in the photoelectric effect experiment can be stopped by applying the voltage of 0.35 V when the radiation 256.7 nm is used. Calculate the work function for silver metal.

Following results are observed when sodium metal is irradiated with different wavelengths. Calculate (a) threshold wavelength and, (b) Planck's constant.

The work function for caesium atom is 1.9 eV. Calculate (a) the threshold wavelength and (b) the threshold frequency of the radiation. If the caesium element is irradiated with a wavelength 500 nm, calculate the kinetic energy and the velocity of the ejected photoelectron.

The longest wavelength doublet absorption transition is observed at 589 and 589.6 nm. Calculate the frequency of each transition and energy difference between two excited states.

Lifetimes of the molecules in the excited states are often measured by using pulsed radiation source of duration nearly in the nano second range. If the radiation source has the duration of 2 ns and the number of photons emitted during the pulse source is 2.5 x 10¹⁵, calculate the energy of the source.

In astronomical observations, signals observed from the distant stars are generally weak. If the photon detector receives a total of 3.15 x 10^-18J from the radiations of 600 nm, calculate the number of photons received by the detector.

Neon gas is generally used in the sign boards. If it emits strongly at 616 nm, calculate (a) the frequency of emission, (b) distance traveled by this radiation in 30 s (c) energy of quantum and (d) number of quanta present if it produces 2 J of energy.

Nitrogen laser produces a radiation at a wavelength of 337.1 nm. If the number of photons emitted is 5.6 x 10²⁴, calculate the power of this laser.

Arrange the following type of radiations in increasing order of frequency: (a) radiation from microwave oven (b) amber light from traffic signal (c) radiation from FM radio (d) cosmic rays from outer space and (e) X-rays.

An ion with mass number 56 contains 3 units of positive charge and 30.4% more neutrons than electrons. Assign the symbol to this ion.

An element with mass number 81 contains 31.7% more neutrons as compared to protons. Assign the atomic symbol.

In Rutherford's experiment, generally the thin foil of heavy atoms, like gold, platinum etc. have been used to be bombarded by the α-particles. If the thin foil of light atoms like aluminium etc. is used, what difference would be observed from the above results?

In Milikan's experiment, static electric charge on the oil drops has been obtained by shining X-rays. If the static electric charge on the oil drop is -1.282 x 10^-18C, calculate the number of electrons present on it.

A certain particle carries 2.5 x 10^-16C of static electric charge. Calculate the number of electrons present in it.

2 x 10⁸ atoms of carbon are arranged side by side. Calculate the radius of carbon atom if the length of this arrangement is 2.4 cm.

If the diameter of a carbon atom is 0.15 nm, calculate the number of carbon atoms which can be placed side by side in a straight line across length of scale of length 20 cm long.

What transition in the hydrogen spectrum would have the same wavelength as the Balmer transition n = 4 to n = 2 of He⁺ spectrum?

Show that the circumference of the Bohr orbit for the hydrogen atom is an integral multiple of the de Broglie wavelength associated with the electron revolving around the orbit.

Using s, p, d notations, describe the orbital with the following quantum numbers.

(a) n = 1, l = 0; (b) n = 3; l =1 (c) n = 4; l = 2; (d) n = 4; l =3.

(i) An atomic orbital has n = 3. What are the possible values of l and ml ?

(ii) List the quantum numbers (ml and l) of electrons for 3d orbital.

(iii) Which of the following orbitals are possible?

1p, 2s, 2p and 3f

Give the number of electrons in the species, H₂ and O_2.

An atom of an element contains 29 electrons and 35 neutrons. Deduce (i) the number of protons and (ii) the electronic configuration of the element.

An electron is in one of the 3d orbitals. Give the possible values of n, l and ml for this electron.

What is the lowest value of n that allows g orbitals to exist?

(i) Write the electronic configurations of the following ions: (a) H^- (b) Na⁺ (c) O^2-(d) F^-

(ii) What are the atomic numbers of elements whose outermost electrons are represented by (a) 3s¹ (b) 2p³ and (c) 3p⁵?

(iii) Which atoms are indicated by the following configurations?

(a) [He] 2s¹ (b) [Ne] 3s² 3p³ (c) [Ar] 4s² 3d¹.

Which of the following are isoelectronic species i.e., those having the same number of electrons?

Na+, K+, Mg2+, Ca2+, S2-, Ar

The mass of an electron is 9.1 x 10^-31 kg. If its K.E. is 3.0 x 10^-25 J, calculate its wavelength.

Calculate the wavelength of an electron moving with a velocity of 2.05 x 10⁷ ms^-1.

The electron energy in hydrogen atom is given by E_n= (-2.18 x 10^-18)/n²J. Calculate the energy required to remove an electron completely from the n= 2 orbit. What is the longest wavelength of light in cm that can be used to cause this transition?

What is the energy in joules, required to shift the electron of the hydrogen atom from the first Bohr orbit to the fifth Bohr orbit and what is the wavelength of the light emitted when the electron returns to the ground state? The ground state electron energy is -2.18 x 10^-11ergs.

Calculate the wave number for the longest wavelength transition in the Balmer series of atomic hydrogen.

(i) The energy associated with the first orbit in the hydrogen atom is -2.18 x 10^-18J atom^-1. What is the energy associated with the fifth orbit?

(ii) Calculate the radius of Bohr's fifth orbit for hydrogen atom.

What is the maximum number of emission lines when the excited electron of an H atom in n = 6 drops to the ground state?

How much energy is required to ionise a H atom if the electron occupies n = 5 orbit? Compare your answer with the ionization enthalpy of H atom (energy required to remove the electron from n =1 orbit).

What is the wavelength of light emitted when the electron in a hydrogen atom undergoes transition from an energy level with n = 4 to an energy level with n = 2?

Electrons are emitted with zero velocity from a metal surface when it is exposed to radiation of wavelength 6800 Ã…. Calculate threshold frequency () and work function (W₀) of the metal.

A 25 watt bulb emits monochromatic yellow light of wavelength of 0.57μm. Calculate the rate of emission of quanta per second.

Electromagnetic radiation of wavelength 242 nm is just sufficient to ionise the sodium atom. Calculate the ionisation energy of sodium in kJ mol^-1

A photon of wavelength 4 x 10^-7m strikes on metal surface, the work function of the metal being 2.13 eV. Calculate (i) the energy of the photon (eV), (ii) the kinetic energy of the emission, and (iii) the velocity of the photoelectron (1 eV= 1.6020 x 10^-19J).

What is the number of photons of light with a wavelength of 4000 pm that provide

Calculate the wavelength, frequency and wave number of a light wave whose period is 2.0 x 10^-10s.

Find energy of each of the photons which

(i) correspond to light of frequency 3 x 10¹⁵ Hz.

(ii) have wavelength of 0.50 Ô¦.

Yellow light emitted from a sodium lamp has a wavelength (λ) of 580 nm. Calculate the frequency (ν) and wave number () of the yellow light.

Write the complete symbol for the atom with the given atomic number (Z) andAtomic mass (A)

(i) Z = 17, A = 35

(ii) Z = 92, A = 233

(iii) Z = 4, A = 9

How many neutrons and protons are there in the following nuclei?

, , , , 

(i) Calculate the total number of electrons present in one mole of methane.

(ii) Find (a) the total number and (b) the total mass of neutrons in 7 mg of ¹⁴C.

(Assume that mass of a neutron = 1.675 x 10^-27kg).

(iii) Find (a) the total number and (b) the total mass of protons in 34 mg of NH₃at STP.

Will the answer change if the temperature and pressure are changed?

(i) Calculate the number of electrons which will together weigh one gram.

(ii) Calculate the mass and charge of one mole of electrons.