Question

How do you write the electron configuration for calcium?

Answer 1

Electronic configuration:-

• Electron configuration of an element shows us how the electrons are distributed in its atomic orbitals.
• The electron configurations of atoms follow a standard notation in which all the atomic subshells that contain electrons (with the number of electrons they hold written in superscript) are placed in a certain sequence.
• For example, the atomic number of Sodium is 11 and its electron configuration is $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^1$.

Aufbau principle:-

• The Aufbau principle states how the electrons are filled in their atomic orbitals of an atom that is in its ground state.
• The principle states that electrons are filled into the atomic orbitals in the increasing order of the orbital energy level.
• According to the Aufbau principle, the available atomic orbitals which have the lowest energy levels are occupied before those which have higher energy levels.
• A diagram is given below which illustrates us the order in which atomic orbitals are filled:

• Here, $‘\mathrm{n}’$refers to the principal quantum number whereas, $‘\mathrm{l}’$refers to the azimuthal quantum number.

Electronic configuration of Calcium:-

• Atomic number of Calcium is 20, that is Calcium has a total of 20 electrons.
• Since 1s orbital can hold a maximum of 2 electrons, so first 2 electrons will fill the 1s orbital, and the next 2 electrons will fill the 2s orbital.
• The next six electrons of Calcium will go in the 2p orbital, as the p orbital can hold up to six electrons.
• The 2p orbital will be completely filled with six electrons and after that, the next two electrons will move up to fill the 3s orbital.
• Similarly in the same fashion, the next 6 electrons will fill up the 3p orbital.
• And lastly, the remaining 2 electrons will be placed in the 4s orbital.
• This filling up of the orbitals with electrons is according to the Aufbau principle.
• Therefore, the electronic configuration of Calcium is$1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^{6}4{\mathrm{s}}^2$.

Therefore, the electronic configuration of Calcium according to the Aufbau principle is$1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^{6}4{\mathrm{s}}^2$.