Chemistry I - Quantum Numbers

How does the value of n limit the value of l?

The value of l can range from 0 to (n-1).

How does the value of l, limit ml?

The value of ml can range from +l to -l

How is the pattern by which subshells are filled as well as the number of electrons within each principal energy level and subshell designated?

They are designated by their electron configuration.

What is the spectroscopic notation of quantum numbers?

This is notation system for the principle and azimuthal numbers. The principle number retains its integer status, but the azimuthal number is converted to a corresponding letter: l = 0 = s l = 1 = p l = 2 = d l = 3 = f

What does the spin quantum number describe?

This refers to the direction of spin that the electrons in the orbitals have. When 2 electrons are in the same orbital they will have opposite spins. Electrons in different orbitals with the same ms have parallel spins.

What does the principle quantum number describe?

This refers to the energy level and radius of the atom's shell. Higher principle means higher energy and larger radius.

What does the magnetic quantum number describe?

This refers to the particular orbital within a subshell where an electron is most likely to be found. The number and shape of the orbitals is dependent on the subshell they are found in.

What does the azimuthal (angular momentum) quantum number describe?

This refers to the shape and number of subshells within a given principle energy level (shell).

What are the 2 values for ms?

+1/2, and -1/2

What are the four Quantum numbers?

1) N - Principle 2) L - Angular 3) Ml -Magnetic 4) Ms - Spin No two electrons within a single atom can have the same 4 quantum numbers according to the Pauli Exclusion Principle. This is because each number relies on the last (Address Example)

Which will fill first, the 5d subshell or the 6s subshell?

6s will fill first and therefore has a lower energy.

How does a flourescent light work?

A florescent substance first becomes excited by higher energy electromagnetic radiation, such as from a UV lamp. The electrons move from their excited higher energy state to their ground state in 2 or more steps. With each step a photon is emitted, and if the wavelength of this photon is in the visible spectra, it will appear as a particular colored light.

What are the possible values for l, if N=3?

If N=3 then there can be *three* subshells, which range from 0 to 2. These would be 0, 1, and 2.

What are the possible values for ml, if l= 2

If l = 2, the d subshell limits the ml values to -2, -1, 0, +1, +2, which means there are five total orbitals.

What is the maximum number of electrons that can be held in a shell?

It is expressed as: 2 x n^2

What is the maximum number of electrons that can be held in a subshell?

It is expressed as: 4 x l +2

True or False: Each orbital contains a maximum number of electrons equal to the number of total electrons of that atom.

False. Each orbital can hold a maximum of 2 electrons irregardless of the element.

True or False: Electrons will fill the orbitals at random.

False. Electrons fill the lowest energy orbitals and only move on to the next orbital once the previous one has been filled. This is referred to as the Aufbau principle.

How do you write the electron configuration of an ion?

For anions, you just add additional electrons following the electron configuration rules. For cations, you remove electrons from the highest n. if multiple subshells are tied to the highest n (1, 2, 3, etc.) then start with highest l (s, p, d, f)

What are the two notable exceptions to electron configuration?

Chromium, and Iron gain more stability from Hund's rule, than from the added energy of following the electron configuration. For this reason Chromium's true elecctron configuiration is: *[Ar]4s1 3d5* NOT [Ar] 4s2 3d4 Iron's true electron configuration is: *[Ar]4s1 3d10* NOT [Ar]4s2 3d9 Other elements in these groups have similar behaviors where one electron from the highest s subshell moves to the highest d subshell.

What does Hund's rule state?

Electrons will choose to half all of the given orbitals of a subshell prior to doubling up. This is because more repulsion exists between electrons on the same orbital in a subshell, than when they are on separate orbitals on the same subshell. Hence, they will leave some orbitals half filled in order to minimize repulsion, therefore increasing stability.

True or False: Paramagnetic materials have paired electrons and therefore repel, whereas diamagnetic materials have unpaired electrons and attract to a magnetic field.

False. When paramagnetic materials enter a magnetic field their unpaired electrons will have parallel spins, and therefore become attracted to a magnet. Diamagnetic materials have all paired electrons and therefore the magnetic field will not cause electrons to have parallel spins causing them to be repelled by the magnet.

True or False: It is impossible to know the location, and momentum of an electron with perfect accuracy.

True. According to the Heisenberg Uncertainty Principle, to know where an electron is would require stopping it's momentum, and to its momentum would require it to move and therefore be unable to identify its location.

How can you quickly determine which subshell will fill first without running through the entire chart?

Using the n + l rule: When adding the n + l of an atom, the atom with the smallest value will fill first, and thus has lower energy. If the n + l are the same, then the subshell with the lowest n will fill first.

What are valence electrons and how do you calculate how many an atom has?

Valence electrons are an atoms "active" electrons and will interact with other valcence elctrosn thus giving an atoms is characteristivc chemiccal behavior. For elements in groups 1 and 2 the highest s orbital contains the valence electrons For elements in groups 13 and 18 the highest s and p orbitals contains the valence electrons For transition metals the highest s and d orbitals contain the valence electrons For the lanthanide and actinide series the highest s and f orbitals contain the valence electrons Elements in period three and below can accept extra electrons into their d orbital and are therefore capable of breaking the octet rule.

What is the electron configuration of Fe3+

[Ar] 3d5 Electrons are first removed from highest n subshell 4s. When the two electrons in this subshell are removed, there are now a 3s, 3p, and 3d subshell. Since they share the highest n (3), we start by taking from the highest l (d).