Electronic structure of atoms

Question 1

quantum number distinguishing the different shapes of orbitals; it is also a measure of the orbital angular momentum

Answer 1

angular momentum quantum number (l)

Question 2

mathematical function that describes the behavior of an electron in an atom (also called the wave function), it can be used to find the probability of locating an electron in a specific region around the nucleus, as well as other dynamical variables

Answer 2

atomic orbital

Question 3

region of space with high electron density that is either four-lobed or contains a dumbbell and torus shape; describes orbitals with l = 2. An electron in this orbital is called a d electron.

Answer 3

d orbital

Question 4

orbitals that have the same energy

Answer 4

degenerate orbitals

Question 5

a measure of the probability of locating an electron in a particular region of space, it is equal to the squared absolute value of the wave function ψ

Answer 5

electron density

Question 6

multilobed region of space with high electron density, describes orbitals with l = 3. An electron in this orbital is called an f electron.

Answer 6

f orbital

Question 7

rule stating that it is impossible to exactly determine both certain conjugate dynamical properties such as the momentum and the position of a particle at the same time. The uncertainty principle is a consequence of quantum particles exhibiting wave-particle duality.

Answer 7

Heisenberg uncertainty principle

Question 8

quantum number signifying the orientation of an atomic orbital around the nucleus; orbitals having different values of ml but the same subshell value of l have the same energy (are degenerate), but this degeneracy can be removed by application of an external magnetic field

Answer 8

magnetic quantum number (ml)

Question 9

dumbbell-shaped region of space with high electron density, describes orbitals with l = = 1. An electron in this orbital is called a p electron

Answer 9

p orbital

Question 10

specifies that no two electrons in an atom can have the same value for all four quantum numbers

Answer 10

Pauli exclusion principle

Question 11

quantum number specifying the shell an electron occupies in an atom

Answer 11

principal quantum number (n)

Question 12

field of study that includes quantization of energy, wave-particle duality, and the Heisenberg uncertainty principle to describe matter

Answer 12

quantum mechanics

Question 13

spherical region of space with high electron density, describes orbitals with l = 0. An electron in this orbital is called an s electron

Answer 13

s orbital

Question 14

set of orbitals with the same principal quantum number n

Answer 14

shell

Question 15

number specifying the electron spin direction, either +½ or −½

Answer 15

spin quantum number (ms)

Question 16

set of orbitals in an atom with the same values of n and l

Answer 16

subshell

Question 17

mathematical description of an atomic orbital that describes the shape of the orbital; it can be used to calculate the probability of finding the electron at any given location in the orbital, as well as dynamical variables such as the energy and the angular momentum

Answer 17

wave function (ψ)

Question 18

Which of the following statements explains why the Bohr model of the atom ultimately did not work?

A) It appealed to our understanding of a planet in orbit.

B) The Heisenberg uncertainty principle was incorrect.

C) Matter does not have wave properties.

D) It required knowing the position and momentum of an electron.

Answer 18

D) It required knowing the position and momentum of an electron.

The Bohr model pictures the electrons as having a definite position and speed; but we now know, based on the Heisenberg uncertainty principle, that we cannot know the position and speed of an electron.

Question 19

The quantum mechanical model of the atom gives up trying to specify the location of the electron and instead shows us what?

Answer 19

The probability of finding the electron

The quantum mechanical model enables us to calculate the probability of finding the electron in a region of space.

Question 20

What information does Schrödinger’s equation combine?

Answer 20

Kinetic energy, potential energy, and wave properties

Schrödinger’s equation combines information about kinetic energy, potential energy, and wave properties into a single equation involving the wave function of an electron.

Question 21

What are the “dips” in the graphs of radial probability distribution for the 2s and 3s states called?

Answer 21

Radial Nodes

They represent spherical regions where the electron is not likely to be found, similar to the nodes in a standing wave.

Question 22

The Heisenberg uncertainty principle states that it is impossible to simultaneously know which two things about of an electron?

Answer 22

Position and momentum

Any attempt to measure the position of an electron disturbs its path, so its momentum cannot be measured precisely at the same time.

Question 23

To which of the following objects is the Bohr model of an atom similar?

A) A planet in orbit around a sun

B) The blades of a rapidly spinning fan

C) A spinning gyroscope

D) A moth flying around a candle flame

Answer 23

A) A planet in orbit around a sun

The Bohr model used the idea of an electron in an orbit around the nucleus, much like a planet orbiting a sun, as the basis, then added restrictions to this model so that it would match observations.

Question 24

In addition to information about kinetic energy and potential energy of an electron, what additional information does the Schrödinger’s equation provide about an electron?

Answer 24

Wave properties

The wave properties of an electron are contained in Schrödinger’swave function, which is part of the wave equation.

Question 25

What is an orbital?

Answer 25

The probability of finding an electron in a region

Question 26

What are the names for the three quantum numbers in the Schrödinger equation?

Answer 26

Principal, angular, magnetic

Question 27

What are the permissible values for the angular quantum number (l) when n = 4?

Answer 27

0, 1, 2, 3

Question 28

How many angular nodes do the d orbitals have?

Answer 28

2

Question 29

What are the values for ml for a d orbital?

Answer 29

−2, −1, 0, 1, 2

Question 30

There are three p orbitals that are aligned with their major axes along the x, y, and z axes. What is the origin of these three p orbitals?

Answer 30

They are the solutions for the three values of the magnetic quantum number.

Question 31

What are the permissible values for the angular quantum number (l) when n = 3?

Answer 31

0, 1, 2

Question 32

What are the values for ml for a p orbital?

Answer 32

−1, 0, 1

Question 33

What are the permissible values for the angular quantum number (l) when n = 2?

Answer 33

0, 1

Question 34

What is the difference between a 2p and a 3p orbital?

Answer 34

The 3p orbital is farther from the nucleus than the 2p orbital.

Question 35

A great deal of time and effort has been put into trying to locate the electrons in an atom. Why is it important to understand where the electrons are?

Answer 35

Knowing where the electrons are allows prediction and understanding of how atoms come together to form molecules.

Question 36

What are legitimate values for the spin quantum number, ms?

Answer 36

The only legitimate values for the spin quantum number are − ½ and +½.

Question 37

Which statement regarding quantum numbers is not correct?

Answer 37

Electrons may have quantum numbers that overlap as long as they are not in the same place at the same time.

The Pauli exclusion principle states that no two electrons can occupy the same location, therefore they cannot have the same set of quantum numbers at the same time.

Question 38

Which set of quantum numbers is possible for the two electrons of helium?

Answer 38

(1, 0, 0, +1/2) and (1, 0, 0, −1/2)

Both electrons are in the 1s orbital (as indicated by the first three numbers), but one has spin up (+½ ) and the other has spin down (−½ ).

Question 39

Which of the following statements best states the Pauli exclusion principle?

Answer 39

Each electron in an atom must have a unique set of quantum numbers describing it.

One way to think of this (although not technically correct) is that two electrons cannot be in the same place at the same time. The reason this is not technically correct is that electrons have wave properties, and are therefore never really in one place at any given time.

Question 40

What is the difference between a 2s orbital and a 2p orbital?

Answer 40

They have different angular momentum quantum numbers.

All s orbitals have an angular momentum quantum number of 0, whereas all p orbitals have an angular momentum quantum number of 1.