16. Ditribution of Electrons in Various shells

What does the principal quantum number (n) represent?

The main energy level or shell of an electron.

What is the maximum number of electrons a shell can hold?

2n^2, where nnn is the principal quantum number.

How many electrons can the first shell (n=1) hold?

Up to 2 electrons.

How many electrons can the second shell (n=2) hold?

Up to 8 electrons.

How many electrons can the third shell (n=3) hold?

Up to 18 electrons.

How many electrons can the fourth shell (n=4) hold?

Up to 32 electrons.

What is the Aufbau principle?

Electrons fill the lowest energy levels first before moving to higher ones.

What is the order of filling orbitals according to the Aufbau principle?

1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p.

How many orbitals and electrons can an s subshell hold?

1 orbital, up to 2 electrons.

How many orbitals and electrons can a p subshell hold?

3 orbitals, up to 6 electrons.

How many orbitals and electrons can a d subshell hold?

5 orbitals, up to 10 electrons.

How many orbitals and electrons can an f subshell hold?

7 orbitals, up to 14 electrons.

What does the Pauli Exclusion Principle state?

No two electrons in an atom can have the same set of four quantum numbers.

What is Hund’s Rule?

Electrons fill degenerate orbitals singly before pairing up.

What is electron configuration notation for Oxygen (atomic number 8)?

1s² 2s² 2p⁴.

What is the electron configuration exception for Chromium (Cr)?

[Ar] 4s¹ 3d⁵ instead of [Ar] 4s² 3d⁴.

What does the periodic table’s arrangement reflect about electron distribution?

Elements in the same group have similar valence electron configurations; elements in the same period have electrons in the same principal energy level.

How do valence electrons affect chemical bonding?

They determine bonding behavior and reactivity.

How do electron distributions affect periodic trends?

They influence properties like atomic radius, ionization energy, and electronegativity.

What does the term "degenerate orbitals" refer to?

Orbitals of the same energy level that are occupied singly according to Hund’s Rule before pairing.