8.1.1 Understanding Electron Spin

Question 1

Understanding Electron Spin

Answer 1

• Review of the Schrödinger atom; knowing where the electrons are likely to be makes it possible to understand how atoms form molecules.
• The Pauli exclusion principle indicates that each electron in an atom must have a unique set of quantum numbers describing it.

Question 2

NOTE

Answer 2

• Review of the Schrödinger atom:
  · Electrons reside in orbitals.
  · Orbitals have characteristic shapes (s, p, d, f).
  · Orbitals describe the electron density
  probability; the absolute position of an electron
  cannot be determined.
  · Orbitals describe how the energies of electrons
  are quantized.
• From Schrödinger, the quantum numbers are the
  principle quantum number (n), the angular quantum number (l), and the magnetic quantum number (m l ).
• The quantum numbers for both the first and second electrons in helium are (1,0,0).
• The Pauli exclusion principle indicates that each electron in an atom must have a unique set of quantum numbers describing it.
• How can the first and second electrons of helium have the same quantum numbers (1,0,0)?
• They do not. The two electrons have different spin.
• Electron spin is the property of an electron, called up or down, describing the interaction of the electron with a
  magnetic field. The electron spin is represented by the
  electron spin quantum number (m s ), which has a value of +1/2 or –1/2.

Question 3

Stern and Gerlach carried out experiments in which a beam of silver atoms was exposed to a large, homogeneous magnetic field. They found that the beam split into two parts. What did the splitting of the beam of silver atoms mean in terms of electrons and magnetic fields?

Answer 3

Electrons in the silver atoms were influenced by the magnetic field depending on their orientation with regard to the field.

Question 4

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

Answer 4

−½ and +½

Question 5

Which quantum number was not predicted through the Schrödinger equation?

Answer 5

electron spin quantum number

Question 6

What forces need to be considered in determining where an electron might be in an atom?

Answer 6

The potential energy, the kinetic energy and the repulsion of like-charged particles

Question 7

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

Answer 7

They have different angular momentum quantum numbers.

Question 8

Which of the following best states the Pauli exclusion principle?

Answer 8

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

Question 9

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 9

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

Question 10

Which statement about Stern and Gerlach’s experiments with silver atoms is not correct?

Answer 10

The experiments showed that the first three quantum numbers were the same for every electron in a given silver atom

Question 11

Which statement regarding quantum numbers is not correct?

Answer 11

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

Question 12

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

Answer 12

(1, 0, 0, +1/2) and (1, 0, 0, −1/2)