Electron Configuration of Calcium (Ca)
What is the electron configuration of Calcium?
The electron configuration of Calcium (Ca, Z=20) is 1s² 2s² 2p⁶ 3s² 3p⁶ 4s². In noble gas shorthand: [Ar] 4s². It has 0 unpaired electron(s) and is a s-block element.
| Symbol | Ca |
| Atomic Number | 20 |
| Full Electron Configuration | 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² |
| Noble Gas Shorthand | [Ar] 4s² |
| Block | s |
| Period | 4 |
| Group | 2 |
| Unpaired Electrons | 0 |
| Exception? | No |
Orbital Filling Order
Following the aufbau principle, the 20 electrons in Calcium fill orbitals in order of increasing energy: 1s (2 electrons), then 2s (2 electrons), then 2p (6 electrons), then 3s (2 electrons), then 3p (6 electrons), then 4s (2 electrons).
Each orbital is filled according to the Pauli exclusion principle (at most 2 electrons per orbital) and Hund's rule (electrons occupy degenerate orbitals singly before pairing).
Noble Gas Shorthand
The inner electrons of Calcium match the configuration of Ar. This allows us to abbreviate the configuration as [Ar] 4s², where [Ar] represents the filled core and the remaining entries show the valence electrons.
Valence Electrons
The valence shell of Calcium contains 2 electrons in the 4s subshell. These outermost electrons determine Calcium's chemical reactivity, bonding behavior, and position in the periodic table as a s-block element in period 4.
Visualize orbital filling with 3D orbital shapes, aufbau principle, and noble gas shorthand for 36 elements.
Explore Calcium in the Electron Configuration ExplorerRelated Topics
Electron Configuration of Potassium
Orbital filling and noble gas shorthand for Potassium
Electron Configuration of Scandium
Orbital filling and noble gas shorthand for Scandium
Electron Configuration of Hydrogen
Orbital filling for Hydrogen (s-block)
Electron Configuration of Helium
Orbital filling for Helium (s-block)
Calcium on the Periodic Table
Full properties and periodic trends for Calcium
Orbital Hybridization
See how atomic orbitals mix to form sp, sp2, and sp3 hybrids