The first period has two orbitals and hence accommodates 2 electrons in it. Thus it justifies the fact that there are two elements in the first period.
An orbital is a three-dimensional description of the most likely location of an electron around an atom. s, p, d, f and so on are the names given to the orbitals that hold the electrons in atoms.
- S orbital is a spherically symmetrical orbital around the atomic nucleus. The energy level increases as we move away from the nucleus; therefore, the orbitals get bigger.
- The p orbitals are dumbbell-shaped. The node in the p orbital occurs at the centre of the nucleus. The p orbital can occupy a maximum of six electrons due to the presence of three orbitals.
- The d orbital is a cloverleaf or two dumbbells in a plane. For d orbital, the value of l=2; thus, the minimum value of principal quantum number n is 3. The value for l cannot be greater than n-1. The values of ml corresponding to d orbital are (–2, –1, 0, +1 and +2) for l = 2; therefore, there are five d orbitals.
- f orbital has diffused shape. For f orbital, the value of l=3; thus, the minimum value of principal quantum number n is 4. The values of ml corresponding to f orbital are (-3,–2, –1, 0, +1, +2, +3). For l = 3, therefore, there are seven f orbitals.