Rules for writing electron-configuration

Electronic configuration or electron configuration of orbitals takes place according to the following rules. The maximum number of electrons in the main quantum shell = 2n2, where n = principal quantum number. Principal quantum shell divided into sub shell s, p, d, f. Therefore, the maximum number of electrons in a subshell = 2(2l +1), where l = 0, 1, 2, 3 for s, p, d, f orbitals respectively. Aufbau building up principle provides the electron filling up process. Hence according to this principle, the orbitals are filled up in the order of increasing energy. Thus orbitals with the lowest energy filled up first while the highest energy orbital filled up in the end.

Energy Level Diagram & Electronic Configuration

It is difficult for the students to remember the orbital energy level diagram according to the increasing energy level. But a trivial and more convenient diagram replaced by it for easy to remember.

Electronic configuration of general chemical elements and energy levels of electron

Therefore, the energy levls of orbitals according to this diagram, 1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 4d < 5p < 6s < 4f < 5d < 6p < 7s < 5f…

Electronic Configuration of s-block Elements

s-block elements consist of one or two-electron or electrons in s-orbital of the outer quantum shell. Since the common feature generates similar chemical properties among the s-block elements. Therefore, the general electronic configuration of s-block elements is ns1→2.

1s-block Chemical Elements

Hydrogen, lithium, sodium, potassium, rubidium, and francium belongs to 1s-block elements in the periodic table with the general electronic configuration of valence electron = ns1.

Atomic Number Chemical Elements Electronic Configuration
1 Hydrogen (H) 1s1
3 Lithium (Li) 1s2 2s1
11 Sodium (Na) [Ne] 3s1
19 Potassium (K) [Ar] 4s1
37 Rubidium (Rb) [Kr] 5s1
55 Cesium (Cs) [Xe] 6s1
87 Francium (Fr) [Rn] 7s1

2s-block Chemical Elements

Beryllium, magnesium, calcium, strontium, barium, and radium belongs to 1s-block elements in the periodic table with general electronic configuration of valence electron = ns2.

Atomic Number Chemical Elements Electronic Configuration
4 Beryllium (Be) 1s2 2s1
12 Magnesium (Mg) 1s2 2s2
20 Calcium (Ca) [Ne] 3s1
38 Strontium (Sr) [Ar] 4s1
56 Barium (Br) [Kr] 5s1
88 Radium (Ra) [Xe] 6s1