Atomic Structure

Uncertainty in the position of an electron (mass=9.1*10^-31kg) moving with a velocity of of 300 ms^-1 accurate upto 0.001% will be:

• 5.76*10^-2 m

• 1.92*10^-2 m

• 3.84*10^-2 m

• 19.2*10^-2 m

The frequency of radiation emitted when an electron falls from n=4 to n=1 in a hyddrogen atom will be:(given, ionisation energy of H=2.18*10^-18 J atom^-1 and h=6.625*10^-34 Js)

• 3.08*10¹⁵ s^-1

• 2.00*10¹⁵ s^-1

• 1.54*10¹⁵ s^-1

• 1.03*10¹⁵ s^-1

The wavelength of the first spectral line in Balmer series of spectrum of H-atom is:

• 36/5R cm

• 5R/36 cm

• 6/R cm

• None of these

Bohr's radius of H-atom is 0.529Å. What is the radius of 2^nd shell of He⁺ ?

• 0.529 Å

• 10.58 Å

• 1.058 Å

• 0.2645 Å

If an electron, a proton and an α-particle have same de Broglie wavelengths, their kinetic energies are related to one another as :

• electron > proton > α-particle

• electron < proton < α-particle

• α-particle > proton > electron

• electron = proton = α-particle

√v of X-rays is plotted v/s atomic numbers of elements in Moseley's experiment. The slope of graph is( a & b are constants) :

• v

• a

• b

• ab

When the letters shown have their usual meanings, the velocity of photoelectrons is:

• [2hc/m {λ₀-λ/λλ₀}] ^1/2

• [2hc/m {λ₀-λ/λλ₀}] ²

• 2hc/m

• (m/2hc)²

The number of electrons in d-subshell of Cr²⁺ (Z=24) is not equal to:

• s-electrons in Ne (Z=10)

• unpaired electrons in Fe (Z=26)

• p-electrons in O (Z=8)

• d-electrons in Fe³⁺ (Z=26)

When an electron jumps from 5th excited state to 2nd excited state in H-atom, the number of lines produced in Balmer series is :

• 2

• 4

• 6

• 0

The quantum numbers of 9th electron in the electronic configuration of fluorine (Z=9), are:

• n=2,l=0,m=0,s=0

• n=2,l=0,m=0,s=+1/2

• n=2,l=1,m=0,s=+1/2

• n=2,l=1,m=1,s=-1/2