Structure of Atom — Practice

Question 1

The maximum number of electrons that can be accommodated in the L shell of an atom is

Accepted Answer

8

Question 2

If l = 1 for an atom, the number of orbitals in its sub-shell is

Accepted Answer

3

Question 3

The quantum number which describes the size and energy of the orbit or shell is

Accepted Answer

n

Question 4

An emission spectrum consists of bright spectral lines on a dark background. Which of the following does not correspond to the bright spectral lines?

Accepted Answer

velocity of light

Question 5

How is an orbital different from a Bohr orbit?

Accepted Answer

A Bohr orbit is a definite, fixed path at a fixed distance from the nucleus, on which the electron is assumed to travel, so its exact position would be known at all times. An orbital is a three-dimensional region of space around the nucleus in which the probability of finding the electron is maximum. There is no defined path, because the position and velocity of an electron cannot both be measured accurately, and consequently the atom has no definite boundary.

Question 6

Answer briefly: (a) maximum electrons in a principal energy level, (b) maximum in a sub-shell, (c) maximum in an orbital, (d) number of sub-shells in a principal energy level, (e) spin orientations possible for an electron in an orbital.

Accepted Answer

(a) 2n squared. (b) 2(2l + 1), so 2 for s, 6 for p, 10 for d and 14 for f. (c) Two, and they must have opposite spins. (d) n sub-shells, since l runs from 0 to n - 1. (e) Two, clockwise and anticlockwise, represented by +1/2 and -1/2.

Question 7

The wavelength of a radio wave is 1.0 m. Find its frequency.

Accepted Answer

Using c = (frequency)(wavelength), frequency = c divided by wavelength = (3 x 10^8 m/s) divided by 1.0 m = 3 x 10^8 Hz, that is 3 x 10^8 reciprocal seconds, or 300 MHz.

Question 8

In an atom the number of electrons in the M shell equals the number in the K and L shells together. Find the outermost shell, the electrons in it, the atomic number, and the electronic configuration.

Accepted Answer

The K shell holds 2 and the L shell holds 8, so K and L together hold 10. The M shell therefore has 10 electrons. Since M can hold up to 18, it is not full, but by the Aufbau rule 4s fills before 3d, so the element is in the fourth period with two electrons in the N shell. (a) The outermost shell is N. (b) It has 2 electrons. (c) The atomic number is 2 + 8 + 10 + 2 = 22. (d) The configuration is 1s2 2s2 2p6 3s2 3p6 3d2 4s2.

Question 9

Write the four quantum numbers for the differentiating electron of a sodium atom.

Accepted Answer

Sodium has Z = 11 and the configuration 1s2 2s2 2p6 3s1. The differentiating electron is the last one added, the 3s electron. Its quantum numbers are n = 3, l = 0, ml = 0, and ms = +1/2 or -1/2.

Question 10

An orbital diagram for nitrogen shows the three 2p electrons with two paired in one orbital and one in another. Which rule does this violate, and what is the correct arrangement?

Accepted Answer

It violates Hund's rule, which states that electron pairing in orbitals begins only when all the available degenerate orbitals of the same energy are singly occupied. Nitrogen has Z = 7 and the configuration 1s2 2s2 2p3. The three 2p electrons must therefore occupy the three separate 2p orbitals singly, with parallel spins, and none of them paired.

Practice — Structure of Atom

Sign in to save attempts to your dashboard and track your accuracy over time

Find a verified tutor

Join a live course

Browse coaching centres

About

Categories

Support

Documentation

Get Study Tips & Updates

Download Our App

Download for iOS

Download for Android

Popular Cities