# Chemistry Class 11 NCERT Solutions: Chapter 2 Structure of Atom Part 7

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Q: 20. Calculate the wavelength of an electron moving with a velocity of.

Answer:

According to de Broglie’s equation,

Where,

Substituting the values in the expression of λ

Hence, the wavelength of the electron moving with a velocity of

Q: 21. The mass of an electron is If its J, calculate its wavelength.

Answer:

From de Broglie’s equation,

Given,

Kinetic energy (K.E) of the electron

Substituting the value in the expression of

Hence, the wavelength of the electron is

Q: 22. Which of the following are isoelectronic species i.e., those having the same number of electrons?

Answer:

Isoelectronic species have the same number of electrons.

Number of electrons in sodium

Number of electrons in

A positive charge denotes the loss of an electron.

Similarly,

Number of electrons in

Number of electrons in

Number of electrons in

A negative charge denotes the gain of an electron by a species.

Number of electrons in sulphur

Hence, the following are isoelectronic species: