Structure of Atom · Question 3

Among the following, the correct statement(s) for electrons in an atom is(are)

1. Uncertainty principle rules out the existence of definite paths for electrons.
2. The energy of an electron in 2s orbital of an atom is lower than the energy of an electron that is infinitely far away from the nucleus.
3. According to Bohr’s model, the most negative energy value for an electron is given by n = 1, which corresponds to the most stable orbit.
4. According to Bohr’s model, the magnitude of velocity of electrons increases with increase in values of n.

Answer

(1) Uncertainty principle rules out the existence of definite paths for electrons., (2) The energy of an electron in 2s orbital of an atom is lower than the energy of an electron that is infinitely far away from the nucleus., (3) According to Bohr’s model, the most negative energy value for an electron is given by n = 1, which corresponds to the most stable orbit.

Solution

(A) Position and momentum cannot both be known exactly, so a definite path (trajectory) is ruled out – correct.

(B) Energy of a free electron at infinity is taken as zero; a bound 2s electron has negative energy, i.e. lower – correct.

(C) En = -13.6 Z2n2 eV is most negative for n = 1, the most stable orbit – correct.

(D) vn = 2.18 106 Zn m s-1, so v decreases as n increases – incorrect.

Answer: (A), (B), (C)