Electron Configuration and Shell Structure

15 question-and-answer flashcards that cover definitions, orbital capacities, electron-configuration rules, transition-metal exceptions, and shorthand notation.

What are electron shells in an atom?

Fixed energy levels surrounding the nucleus where electrons are found, each identified by a principal quantum number.

How does distance from the nucleus relate to shell energy?

The farther a shell is from the nucleus, the higher its energy.

Into what sub-shells are electron shells divided?

s, p, d, and f sub-shells.

How many orbitals and electrons can the s sub-shell hold?

1 orbital that can hold 2 electrons.

How many orbitals and electrons can the p sub-shell hold?

3 orbitals that can hold a total of 6 electrons.

How many orbitals and electrons can the d sub-shell hold?

5 orbitals that can hold a total of 10 electrons.

How many orbitals and electrons can the f sub-shell hold?

7 orbitals that can hold a total of 14 electrons.

How many electrons can the first four shells hold?

1st: 2, 2nd: 8, 3rd: 18, 4th: 32.

What does the sub-shell notation 1s² 2s² 2p⁶ indicate?

2 electrons in the 1s orbital, 2 in the 2s, and 6 in the 2p orbital.

State the three rules for writing electron configurations.

(1) Electrons fill the lowest-energy sub-shells first (Aufbau). (2) Electrons occupy orbitals singly before pairing (Hund’s rule). (3) For ions, add or remove electrons from the highest-energy orbital.

In electron box-orbital diagrams, what do up and down arrows represent?

Electrons with opposite spins occupying the same orbital.

Why are chromium and copper exceptions to expected configurations?

They each promote a 4s electron to the 3d sub-shell (Cr: 3d⁵4s¹, Cu: 3d¹⁰4s¹) to gain extra stability.

When transition metals form ions, which electrons are lost first?

The 4s electrons are removed before the 3d electrons.

How does outer-shell electron count influence chemical properties?

S-block elements lose outer electrons easily, while p-block elements tend to gain electrons to form negative ions.

What is noble-gas shorthand in electron configurations?

A notation that uses a noble gas symbol to represent filled inner shells, e.g., [Ar] 4s² 3d¹⁰ instead of writing the full configuration.