8.1.4 Electron Configurations Beyond Neon

Question 1

Electron Configurations Beyond Neon

Answer 1

• Each orbital holds two electrons, the s orbital for a given energy level is lower in energy than the p orbitals, and one electron enters each degenerate orbital before any pairing occurs.
• By the aufbau principle, the ground state electron configurations for atoms beyond hydrogen are found by filling orbitals in successive order.
• The periodic table is arranged in blocks of elements with similar valence electron configurations.

Question 2

note

Answer 2

• By the Pauli exclusion principle, each orbital can only hold two electrons. The two electrons differ only in
  electron spin quantum number (m s ).
• For a given energy level in elements beyond hydrogen, the s orbital is lower in energy than the p orbitals. This is due to electron shielding. The s orbital therefore fills before the p orbitals.
• By Hund’s rule, one electron enters each degenerate orbital (such as the 2p orbitals) before any pairing occurs. These electrons tend to have aligned electron spins.
• By the aufbau principle, the ground state electron
  configurations for atoms beyond hydrogen are found by filling orbitals in successive order, from lowest energy to highest energy.
• The electron configuration for neon (Ne) is 1s 2 2s 2 2p 6 . This is referred to as the neon core, and is represented by [Ne] in the electron configuration for elements beyond neon. Similarly, the electron configuration for argon is called the argon core ([Ar]).
• Due to electron shielding, the 4s orbital is lower in energy than the 3d orbitals for most elements. Therefore, the 4s orbital fills before the 3d orbitals.
• For example, the 4s orbital of scandium (Sc) fills before the 3d orbital. Therefore, the electron configuration of scandium is [Ar]4s 2 3d 1 .
• The periodic table is arranged in blocks of elements with similar valence electron configurations.
• The s block consists of elements in groups 1 and 2 on the periodic table, as well as helium. The s block is characterized by having valence electrons in s orbitals.
• The p block consists of elements in groups 13 through 18 on the periodic table, and is characterized by having valence electrons in p orbitals.
• The d block consists of elements in groups 3 through 12 on the periodic table, and is characterized by having valence electrons in d orbitals.
• The f block consists of the lanthanide series and the
  actinide series. The f block is characterized by having
  valence electrons in f orbitals.

Question 3

What is the maximum number of electrons in a 3d set of orbitals?

Answer 3

10

Question 4

Which of the following represents the ground state electron configuration of a neutral calcium atom?

Answer 4

Ca: 1s2 2s2 2p6 3s2 3p6 4s2

Question 5

What is the electron configuration of sodium ion (Na+ )?

Answer 5

[ Ne]

Question 6

Which of the following is a p block element?

Answer 6

sulfur

Question 7

Which of the following is the best explanation of why the orbital of the 4s energy sublevel is, in general, lower than the orbitals of the 3d energy sublevel in electron orbital filling following the aufbau principle?

Answer 7

The orbital in the 4s energy sublevel experiences less electron shielding, and thus experiences a greater degree of effective nuclear charge than the 3d orbitals.

Question 8

Which of the following is the best electron configuration of a gaseous sample of chromium?

Answer 8

Cr: [Ar] 4s1 3d5

Question 9

What is the ground state electron configuration of scandium?

Answer 9

[Ar] 4s2 3d1

Question 10

Which of the following best illustrates the aufbau principle?

Answer 10

Electrons filling up existing orbitals in an expected arrangement

Question 11

What is the ground state electron configuration of manganese?

Answer 11

[Ar] 4s2 3d5

Question 12

What is the ground state electron configuration of aluminum?

Answer 12

[ Ne] 3s2 3p1