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Write different isotopes of oxygen, carbon and chlorine.

What was the basis for the proposal of Dalton's atomic theory?

1. What are A, B, C, D and E in the given figure?
2. What is the purpose of C?
3. Explain the role of D in the phenomenon taking place in the discharge tube.

An atom of an element is represented as ${}_{\mathrm{Z}}\mathrm{X}^{\mathrm{A}}$. After the emission of $\mathrm{\beta }-\mathrm{particle}$, another elemnt Y is formed. Represent Y with atomic number and mass number.

Calculate the specific charge (e/m) of the following particles and then arrange the particle in the ascending order of their specific charges.
1. electron
2. proton
3. $\mathrm{\alpha }-\mathrm{particle}$

Calculate the mass of a charged particle in CGS units if its charge is x coulomb and specific charge is $\mathrm{\gamma }$ coulomb/g.

The isotopes of an element have mass numbers : A, A+1, A+2. The ratio of abundance of these isotopes is 3:2:4. Calculate the average atomic mass of the element.

Following conclusions are drawn by observing $\mathrm{\alpha }$-ray scattering experiment. Write the respective observations based on which these conclusions are drawn.
1. Non-uniform distribution distribution of positive charge.
2. Presence of positively-charged core or nucleus.
3. Presence of large empty space in atom.

Compare: Thomson's atomic model with Rutherford's atomic model.

The wavelength of particular radiation in 700 nm (1nm = ${10}^{-9}$m). Find its frequency (v). 

An element has protons whose mass is equal to 23,881 time that of an electron. Identify the element and write its electronic configuration.

Write the electronic configuration and the atomic number of the atom which becomes stable by gainig 3 electrons in fifth shell.

What is the ratio of the amount of energy required to remove an electron from hydrogen and ${\mathrm{He}}^{+}$ ion?

Complete the following table:
Valence shells           Charges on          Electronic configu-           Number of electrons in         Number of core
 in atom                      stable ions           ration of elements             penultimate shell                   electrons
    
     M                                   +3               
                                           +1                                                                           8                                             18
     N                                    +2                                                                                                                          18
                                                                             2, 8, 6
Note: Core electrons are inner electrons which exclude valence electrons.

According to Thomson's atomic model, electrons revolve round the nucleus.

In a discharge tube, node rays originate when electrons collide with gas molecules.

${}_8\mathrm{O}^{16} \mathrm{and} {}_8\mathrm{O}^{18}$ are isotopes while ${}_{20}\mathrm{Cl}^{40} \mathrm{and} {}_{18}\mathrm{Ar}^{40}$ are isobars.

Energy is absorbed when the lectron jumps from K to L energy shells.

$\mathrm{\alpha }-\mathrm{ray}$ scattering experiment proved that the positive particles are present in the extra nuclear part of an atom.

Characteristics spectra of atoms are line spectra.

An electron in the excited state of an atom is higly unstable.

Anode rays are deflected towards the negative plate in the presence of an electric field because they consist of ________ particles.

Some of the $\mathrm{\alpha }-\mathrm{rays}$ deflect in acute and obtuse angles due to the presence of the ________ in the centre of the atom.

According to classical electrodynamics, if an electrically charged particle revolves in a circular path, it continously ______energy.

The energy of an electron present in the first orbit of an atom is ______ than the energy of electron in the other orbits.

Splitting of spectral lines in the presence of magnetic field is known as _______ effect.

The kinetic energy of an electron present in the first orbit of an atom is __________ than that of the electron in the last orbit.

The spectra produced by the deexcitation of an electron is called_________.

Which of the following concepts was not considered in Rutherford's atomic model?
1. the electrical neutrality of atom.
2. the quantisation of energy
3. alectrons revolve around nucleus at very high speeds.
4. existence of nuclear forces of attraction on the electrons.

When alpha particles are sent through a thin metal foil, only out of ten thousand of them rebounded. This observation led to the conclusion that 
1. positively-charged particles are concentrated at the centre of the atom
2. more number of electrons is revolving around the nucleus of the atom.
3. unit positive charge is only present in an atom.
4. a massive sphere with more negative charge and unit positive charge is present at the centre of the atom.

Canal ray experiment lead to the discovery of _________
1. protons
2. neutrons
3. electrons
4. nucleus

In which of the following pairs of shells, energy diference between two adjacent orbits in minimum?
1. K, L
2. L, M
3. M, N
4. N, O

Assertion A : An electron in the inner orbit is more tightly bound to the nucleus.
Reason B : The greater the absolute value of energy of an electron the more tightly the electron is bound to the nucleus.
1. Both A and B are true but B is not the appropriate reason for A.
2. Both A and B are individually correct and B is the correct reason for A.
3. A is correct but B is not correct.
4. Both A and B are not correct.

The electrono revolves only in the orbits in which 
1. $\mathrm{mvr}>\frac{\mathrm{nh}}{2\mathrm{\pi }}$
2. $\mathrm{mvr}\ge \frac{\mathrm{nh}}{2\mathrm{\pi }}$
3. $\mathrm{mvr}=\frac{\mathrm{nh}}{2\mathrm{\pi }}$
4. $\mathrm{mvr}<\frac{\mathrm{nh}}{2\mathrm{\pi }}$

Which among the following pairs are having different number of valence electrons?

If two naturally occuring isotoped of an element are $7^{\mathrm{X}15}, 7^{\mathrm{X}11};$ what will be the percentage composition of each isotope of X occuring, respectively, if the average atomic weight accounts to 14?
1. 95, 5
2. 80, 20
3. 75, 25
4. 65, 35 

According to quantum theory of radiation, which is false?
1. radiations are associated with energy
2. radiation is neither emitted nor absorbed discontinously
3. the magnitude of energy associated with a quantum is dependent on frequency.
4. photons are quanta of radiation.

Select True/ False among the following statements:
(i) Bohr's theory successfully explained stability of the atom.
(ii) Atoms give line spectra.
(iii) Velocity of electromagnetic waves depends on the frequency.
(iv) Bohr introduced the concept of orbital.
1. (i) T, (ii) T, (iii) F, (iv) F
2. (i) T, (ii) F, (iii) T, (iv) T
3. (i) F, (ii) T, (iii) F, (iv) F
4. (i) F, (ii) F, (iii) T, (iv) T

Which of the following particles do not produce electronic spectra?
1. ${\mathrm{Li}}^{+2}$
2. ${\mathrm{He}}^{+2}$
3. ${\mathrm{Be}}^{+2}$
4. ${\mathrm{Na}}^{+}$

An element has two isotopes with mass numbers 16 and 18. The average atomic weight is 16.5. The percentage abundance of these isotopes is ______ and ______, respectively.
1. 75, 25
2. 25, 75
3. 50, 50
4. 33.33, 66.67

Which among the following are isobars?
1. ${}_{\mathrm{b}}X^a and {}_{b}Y^{a+1}$
2. ${}_{\mathrm{b}}\mathrm{X}^{\mathrm{a}} \mathrm{and} {}_{\mathrm{c}}\mathrm{Y}^{\mathrm{b}}$
3. ${}_{\mathrm{b}}\mathrm{X}^{\mathrm{a}} \mathrm{and} {}_{\mathrm{b}+1}\mathrm{Y}^{\mathrm{a}}$
4. ${}_{\mathrm{b}}\mathrm{X}^{\mathrm{a}} \mathrm{and} {}_{\mathrm{b}-1}\mathrm{X}^{\mathrm{a}-1}$

Some of the elements have fractional atomic masses. The reason for this could be
1. the existence of isobar
2. the existence of isotopes
3. the nuclear reaction
4. the presence of neutrons in the nucleus

Which of these pairs has almost similar masses?
1. proton-electron
2. neutron-electron
3. electron-${}_1\mathrm{H}^1$
4. Neutron -${}_1\mathrm{H}^1$

The energy of an electron revolving in the $3^{\mathrm{rd}}$ orbit of ${\mathrm{Be}}^{+3}$ ion is ________ev
1. -10.2
2. -13.6
3. -24.4
4. -18.1

Which of the following concepts, was not considered in Rutherford's atomic model?
1. the electrical neutrality of atom
2. the quantisation of energy
3. electrons revolve around the nucleus at very high speeds
4. existence of nuclear forces of attraction on the electrons

${}_7\mathrm{X}^{15}, {}_7\mathrm{X}^{11}$ are two naturally occuring isotopes of an element X. What is the percentage of each isotope of X if the average atomic mass is 14?
1. 95, 5
2. 80, 20
3. 75, 25
4. 65, 35

A negative ion of an element has 8 electrons in its M shell. The atomic number of the element is 
1. 15
2. 18
3. 20
4. 16

Arrange the following statements given by the various scientists in chronological order.
(i) calculation of energy and radius of orbit.
(ii) atoms of the same elements are identical in all respect
(iii) calculation of diameter of the nucleus and the atom
(iv) assumption of thinly spread positively-charged mass
1. (iv), (iii), (i), (ii)
2. (iv), (ii), (iii), (i)
3. (ii), (iv), (iii), (i)
4. (iii), (iv), (ii), (i)

What is the ratio of the radii of the first successive odd orbits of hydrogen atom?
1. 9 : 1
2. 1 : 9
3. 1 : 3
4. 3 : 1

An electron revolves round the nucleus in the 3rd orbit and jumped to a higher orbit X showing a difference in angular momentum equal to $\frac{\mathrm{h}}{\mathrm{\pi }}$. The value of 'X' could be
1. 4
2. 6
3. 5
4. 7

Rutherford's $\mathrm{\alpha }-\mathrm{particle}$ scattering experiment eventually led to the conclusion that
1. mass and energy are related 
2. the point of impact with matter can be precisely determined 
3. neutrons are burried deep in nucleus
4. electrons are distributed in  a large space around the nucleus

Arrange the following steps which are carried out in $\mathrm{\mu }-\mathrm{ray}$ experiment in the correct sequence:
a. Passage of $\mathrm{\mu }-\mathrm{particles}$ through a slit
b. bombardment of $\mathrm{\mu }-\mathrm{particles}$ with a gold foil.
c. defletion of $\mathrm{\mu }-\mathrm{particles}$
d. production of $\mathrm{\mu }-\mathrm{particles}$
1. d a b c
2. d a c b
3. a d c b
4. a d c b

Which among the following pairs are having different number of total electrons?
1. ${\mathrm{Na}}^{+} \mathrm{and} {\mathrm{Al}}^{+3}$
2. ${\mathrm{P}}^{-3} \mathrm{and} \mathrm{Ar}$
3. ${\mathrm{Mg}}^{+2} \mathrm{and} \mathrm{Ar}$
4. ${\mathrm{O}}^{-2} \mathrm{and} {\mathrm{F}}^{-}$

The postulates of Bohr's atomic model are given below. Arrange then in the correct sequence:
a. As long as the electron revolves in a particular orbit, the electron does not lose its energy. Therefore, these orbits are called stationary orbits and the electrons are said to be in stationary energy states.
b. Electrons revolve around nucleus in specified circular paths called orbits or shells.
c. The energy associated with a certain energy level increases with the increase of its distance from the nucleus.
d. An electron jumps from a lower energy level to a higher energy level by absorbing energy. But when it jumps from a higher to lower energy level, energy is emitted in the form of electromagnetic radiation.
e. Each orbit or shell is associated with a definite amount of energy. Hence, these are also called energy levels and are designated as K, L, M and N, respectively.
1. a c d e b
2. b c e a d
3. b e c a d
4. b a d c e

The ratio odf atomic numbers of two elements A and B is 1:2. The number of electrons present in the valence shell ($3^{\mathrm{rd}}$) of A is equal to the difference in the number of electrons present in the other two shells. Steps involved for the calculation of ratio of number of electrons present in a penultimate shell to anti-penultimate shell of B are given below. Arrange them in the correct sequence:
a. calculation of atomic number of B
b. calculation of valence electrons present in A
c. calculation of atomic number of A
d. calculation of number of electron present in the penultimate and anti-penultimate shells of B.
e. writing electronic configuration of B
1. b c d a e
2. b c a e d
3. d e b c a
4. d b a c e

The equation given by Bohr to calculate radius of ${\mathrm{n}}^{\mathrm{th}}$ orbit of hydrogen atom is 
1. ${\mathrm{r}}_{\mathrm{n}}=\frac{{\mathrm{n}}^2{\mathrm{h}}^2}{4{\mathrm{\pi }}^2\mathrm{me}}$
2. ${\mathrm{r}}_{\mathrm{n}}=\frac{{\mathrm{n}}^2{\mathrm{h}}^2}{4{\mathrm{\pi }}^2{\mathrm{me}}^2}$
3. ${\mathrm{r}}_{\mathrm{n}}=\frac{{\mathrm{nh}}^2}{4{\mathrm{\pi }}^2\mathrm{me}}$
4. ${\mathrm{r}}_{\mathrm{n}}=\frac{{\mathrm{n}}^2{\mathrm{h}}^2}{4{\mathrm{\pi }}^2{\mathrm{m}}^2\mathrm{e}}$

The number of electron present in valence shell of an atom with atomic number 38 is
1. 2
2. 10
3. 1
4. 8

The mass number of an atom whose unipositive ion has 10 electrons and 12 neutrons is
1. 22
2. 23
3. 21
4. 20

When the same isotopic gas is taken in two discharge tubes, the angle of deflection is found to be different though the strength of the external electric field applied is the same. Explain.

In a canal ray experiment different gases were found to produce canal rays with the same specific charge. Explain.

When canal rays experiment is condicted with hydrogen gas, scientists were found to give particles with different $\frac{e}{m}$ values. Justify.

Energy of the electron in the atom is negative. Explain.
[Hint : Energy of a free electron is taken as zero.]

Electronic spectra can distinguish isobars but not isotopes. Justify.

If the energy difference between the orbits when an electron in H atom gets excited to higher energy orbit from its ground state is 12.1 eV/ atom, calculate the frequency of radiation emitted $(1 \mathrm{eV}=1.602\times {10}^{-19} \mathrm{J})$ when electron comes back to second energy level.

Is the enregy difference between successive orbits the same for all orbits? Justify your answer.

Though there is only one electron in a hydrogen atom, the spectrum of hydrogen contains a number of lines. How do you explain this?

What is the ratio of the radius of the $1^{\mathrm{st}}$orbit to $2^{\mathrm{nd}}$ orbit, if the velocity of the lectron in the $1^{\mathrm{st}}$ orbit is twice that of the $2^{\mathrm{nd}}$ orbit.

A particular atom has the 4th shell as its valence shell. If the difference between the number of electrons between K and N shells and L and M shells is zero, find the atomic number of the element and electronic configuration of its stable ion.

A stable unipositive ion of an element contains three fully filled orbits. What is the atomic number of the element?

Explain why a blackened platinum strip when placed at the radius of curvature turns red hot, only when the cathode taken has concave shape.

The average atomic mass of two isotopes with mass numbers A and A+2 is A+0.25. Calculate the percentage abundance of the isotopes.

Spectral line given by an atom is a kind of signature of the respective atom. Comment on this statement.

Why was a spherical sulphide screen used in $\mathrm{\alpha }-\mathrm{ray}$ scattering experiment?

Why is the source of $\mathrm{\alpha }-\mathrm{particles}$ kept inside the lead block?

If Thomson's model is considered to be correct, what would be the observation of Rutherford's $\mathrm{\alpha }-\mathrm{ray}$ scattering experiment?

The ratio of the atomic numbers of two elements A and B is 2:3. A is an inert gas with the first 3 orbits completely filled. Identify A and B and write their electronic configuration.

A stable dipositive ion and a dinegative ion are isoelectronic with an octet configuration in the second shell of their atoms. Identify the preseding and succeeding elements and write their electronic configuration.

Predict the possible atomic number(s) of an atom in which the third shell is incompletely filled and maximum 3 more electrons can be added in that shell.

The radius of ${\mathrm{n}}^{\mathrm{th}}$ orbit of a single electron species is $0.132 {\mathrm{n}}^2{\mathrm{A}}^{°}$. Identify the element.

What is the frequency of light emitted when an electron in a hydrogen atom jumps from the $3^{\mathrm{rd}}$ orbit to the $2^{\mathrm{nd}}$ orbit?

An electron having an angular momentum of $1.05\times {10}^{-34}$ Joules jumps to another orbit such that it has an angular momentum of $4.20\times {10}^{-34}$ joules. Explain the possible transitions.

The mass number of a particular element which has equal number of protons and neutrons is 32. What is the electronic configuration of the atom and its stable ion?

In Millikan's oil drop experiment, the distance between the metal plates, A and B to which an electric potential is applied such that A is positive and B is negative is 5 mm. An oil drop is found to be suspended at a distance of 2 mm from B. Predict the change in the position of the oil drop when there is a sudden drop or rise in potential. Justify.

Different gases in the discharge tube produce different colours under suitable conditions of pressure and voltage. Explain.

Is the velocity of an electron in all orbits the same for an atom of a particular element? How does it vary for different single electron species? Give reasons in support of your answer.

What is the ratio of distance successive orbits of 1 and 2 to 2 ans 3 of hydrogen atom?

If ${}_{\mathrm{x}}{}^{\mathrm{y}}\mathrm{A}^{+1} \mathrm{or} {}_{\mathrm{x}-1}{}^{\mathrm{y}-2}\mathrm{B}^{+1}$ were to be used instead of $\mathrm{\alpha }-\mathrm{particle}$ in Rutherford's experiment, which would be better and why?

Draw a comparison between the potential energy and kinetic energy of electrons in the $1^{\mathrm{st}}$ orbits of hydrogen and ${\mathrm{He}}^{+}$ ion. Also comment on the total energy of the electrons in the above cases.

Though the kinetic energy of electrons decreases with an increase in the distance from the nucleus, the potential energy of the electron increases. How do you account for this?

Why is high voltage and low pressure maintained in the discharge tube?

If canal ray experiments are conducted with different isotopes of hydrogen gas, do the canal rays produced show the same deflection under the external electric field? Give reasons to support your answer.

If the given schematic diagram represents Thomson's experiment and the corresponding observation, what would be his atomic model?