# 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 for this electron.

Answer:

For the orbital:

Principal quantum number

Azimuthal quantum number

Magnetic quantum number

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.

(ii) The electronic configuration of the atom is

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

Answer:

Number of electrons present in hydrogen molecule

Number of electrons present in oxygen molecule

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

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

(iii) Which of the following orbitals are possible?

Answer:

For a given value of

For a given values.

(ii) For 3d orbital,

For a given value of

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

For p-orbital.

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

Similarly,

For f-orbital,

For, the minimum value of n is.

Hence, 1p and 3f do not exist.

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

(a)

Answer:

(a)

(b) For and

The orbital is.

(c) For

The orbital is.

(d) For

The orbital is.

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

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.

(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.