Question

If the radius of first orbit of H is 0.53Å, then radius of fourth orbit of Be3+ will be :
(1) 0.53 A
(2) 2.12A
(3) 3.148A
(4) None​

Answer 1

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Chemistry

Structure of Atom

Bohr's Model for Hydrogen Atom

The radius of first Bohr or...

CHEMISTRY

The radius of first Bohr orbit of hydrogen atom is 0.529

A

˚

. Calculate the radii of (i) the third orbit of He

+

ion and (ii) the second orbit of Li

2+

ion.

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ANSWER

Let us consider the n

th

bohr orbit,

r

n

=

4π

2

mZe

2

n

2

h

2

For hydrogen atom z=1, first orbit n=1

r

1

=

4πr

2

me

2

h

2

=0.592A

0

(i)For He

+

ion,Z=2,thirdorbit,n=3

r

3

(He

+

)=

4π

2

m×2×e

2

3

2

h

2

=

2

9

[

4π

2

me

2

h

2

]

=

2

9

×0.592

=2.380A

0(ii) For Li

2+

ion,Z=3,secondorbitn=2

r

2

(Li

2+

)=

4π

2

m×3×e

2

2

2

h

2

=

3

4

[

4π

2

me

2

h

2

]

= 0.705A

0