Chemistry Class 11 NCERT Solutions: Chapter 2 Structure of Atom Part 9

Q: 25. An electron is in one of the 3d orbitals. Give the possible values of n, l and Equation for this electron.

Answer:

For the Equation orbital:

Principal quantum number Equation

Azimuthal quantum number Equation

Magnetic quantum number Equation

Q: 26. An atom of an element contains 29 electrons and 35 neutrons. Deduce (i) the number of protons and (ii) the electronic configuration of the element.

Answer:

(i) For an atom to be neutral, the number of protons is equal to the number of electrons.

Equation

(ii) The electronic configuration of the atom is

Equation

Q: 27. Give the number of electrons in the species Equation

Answer:

Equation

Number of electrons present in hydrogen molecule Equation

Equation

Equation

Number of electrons present in oxygen molecule Equation

Equation

Q: 28 (i) An atomic orbital has Equation what are the possible values of Equation

(ii) List the quantum numbers Equation of electrons for 3d orbital.

(iii) Which of the following orbitals are possible?

Equation

Answer:

Equation

For a given value of Equation

Equation

Equation

For a given Equation values.

Equation

Equation

Equation

Equation

Equation

Equation

Equation

Equation

(ii) For 3d orbital, Equation

For a given value of Equation

Equation

Equation

(iii) Among the given orbitals only 2s and 2p are possible. 1p and 3f cannot exist.

For p-orbital Equation .

For a given value of n, l can have values from zero to Equation .

Equation

Similarly,

For f-orbital, Equation

For Equation , the minimum value of n is Equation .

Hence, 1p and 3f do not exist.

Q: 29. Using s, p, d notations, describe the orbital with the following quantum numbers.

(a) Equation

Equation

Equation

Equation

Answer:

(a) Equation

Equation

(b) For Equation and Equation

The orbital is Equation .

(c) For Equation

The orbital is Equation .

(d) For Equation

The orbital is Equation .

Q: 30. Explain giving reasons, which of the following sets of quantum numbers are not possible.

Equation

Answer:

(a) The given set of quantum numbers is not possible because the value of the principal quantum number (n) cannot be zero.

(b) The given set of quantum number is possible.

(c) The given set of quantum numbers is not possible.

For a given value of n, ‘l’ can have values from zero to (n-1).

For Equation .

(d) The given set of quantum numbers is possible.

(e) The given set of quantum numbers is not possible.

For n=3

l=0 to (3-1)

l=0 to 2 i.e., 0, 1, 2

(f) The given set of quantum numbers is possible.

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