# Chemistry Class 11 NCERT Solutions: Chapter 2 Structure of Atom Part 2

Q: 3. How many neutrons and protons are there in the following nuclei?

Atomic mass = 13

Atomic number = Number of protons = 6

Number of neutrons = (Atomic mass) -(Atomic number)

Atomic mass = 16

Atomic number = 8

Number of protons = 8

Number of neutrons = (Atomic mass) (Atomic number)

Atomic mass = 24

Atomic number = Number of protons = 12

Number of neutrons = (Atomic mass) (Atomic number)

12 = 12

Atomic mass = 56

Atomic number = Number of protons = 26

Number of neutrons = (Atomic mass) (Atomic number)

26 = 30

Atomic mass = 88

Atomic number = Number of protons = 38

Number of neutrons = (Atomic mass) - (Atomic number)

Q: 4. Write the complete symbol for the atom with the given atomic number (Z) and Atomic mass (A)

(i)

(ii)

(iii)

(i)

(iii)

Q: 5 Yellow light emitted from a sodium lamp has a wavelength Calculate the frequency and wave number of the yellow light.

From the expression,

We get,

Where,

Wavelength of yellow light

Substituting the values in expression (i):

Thus, frequency of yellow light emitted from the sodium lamp

Wave number of yellow light,

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