Decrease in atomic number is not observed during from Chemistry

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 Multiple Choice QuestionsMultiple Choice Questions

231.

The energy of second Bohr orbit of the hydrogen atom is -328 kJ mol-1; hence the energy of fourth Bohr orbit would be

  • -41 kJ mol-1

  • -1312 kJ mol-1

  • -164 kJ mol-1

  • -82 kJ mol-1


232.

If the energy difference between the ground state of an atom and its excited state is 4.4× 10-4J, the wavelength of photon required to produce the transition :

  • 2.26 × 10-12m

  • 1.13 × 10-12m

  • 4.52× 10-16m

  • 4.52 × 10-12m


233.

Which of the following sets of qunatum numbers correct?

  • n =5, l=4, m=0, s=+1/2

  • n= 3, l=3, m=+3, s= +1/2

  • n=6, l=0, m=+1, s= =1/2

  • n=4, l= 2, m=+2, s=0


234.

An electron from one Bohr stationary orbit can go to next higher orbit

  • by emission of electromagnetic radiation

  • by absorption of any electromagnetic radiation

  • by absorption of electromagnetic radiation of particular frequency

  • without emission or absorption of electromagnetic radiation


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235.

Splitting of spectrum lines in magnetic field is

  • Stark effect

  • Raman effect

  • Zeeman effect

  • Rutherford effect


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236.

Decrease in atomic number is not observed during

  • β- emission

  • α- emission

  • positron emission

  • electron capture


A.

β- emission

(a) Axy α- emission (He42)Bx-2y-4

During alpha-emission, atomic number is decreased by two units and atomic mass is decreased by four units.

(b) AxyAx-1y + e°+1positron

when a positron is emitted, there is a decrease in atomic number of one unit while atomic mass remains the same.

(c) AxyAx+1y + e°-1β- particle

During Beta-emission, atomic number is increased by one unit while atomic mass remains the same.

(d) Axy K capture Ax-1y 

During K electron capture, atomic number is decreased by one unit while atomic mass remains unaffected.

Hence, decrease in aotmic number is not observed during Beta-emission.


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237.

According to Bohr's theory, the angular momentum for an electron in 5th orbit is

  • 2.5 h/ π

  • 5 h/ π

  • 25 h/ π

  • π/ 2h


238.

If a species has 16 protons, 18 electrons and 16 neutrons, the symbol (with charge) of species is

  • S-

  • Si2-

  • P3-

  • S2-


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239.

'No two electrons in an atom can have the same set of  quantum numbers.' This principle is known by which one of the following?

  • Zeeman's exclusion principle

  • Stark's exclusion principle

  • Pauli's exclusion principle

  • Hersbach's exclusion principle


240.

Consider the ground state of Cr atom (Z= 24). The numbers of electrons with the azimuthal quantum numbers, = 1 and 2 are respectively

  • 12 and 4

  • 12 and 5

  • 16 and 4

  • 16 and 5


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