Question

The first period has how many orbitals?

Answer 1

An orbital is a three dimensional space around the atomic nucleus where probability of finding an electron is maximum. An orbital can accommodate a maximum of two electrons. s, p, d, f and so on are the orbitals in which the electron can accommodate.

Complete answer:
An orbital is a three dimensional space around the atomic nucleus where probability of finding an electron is maximum. The first period has one orbital which is s orbital where s signifies spherical shape. An orbital can accommodate a maximum of two electrons and therefore the first period contains two elements which are hydrogen and helium. The atomic number, chemical symbol and electronic configuration of hydrogen is $1$, $H$and $1{{s}^{1}}$respectively. Similarly, the atomic number, chemical symbol and electronic configuration of helium is $2$, $He$and $1{{s}^{2}}$, respectively. In electronic configuration, $1$represents the principal quantum number which describes the energy shell of the orbital. In contrast to hydrogen, Helium has complete duplet and thus is chemically unreactive. While hydrogen is a reactive element.

Additional information:
p-orbitals have dumbbell shaped and contain three orbitals. Therefore, a maximum of six electrons can accommodate in p orbitals. d-orbitals have double dumbbell shaped and contain five orbitals. Therefore, a maximum of ten electrons can accommodate in d orbitals. f-orbitals have diffused shape and contain seven orbitals. Therefore, a maximum of fourteen electrons can be accommodated in f-orbitals.

Note:
It is important to note that the first period has one orbital. An orbital can accommodate two electrons only. Thus the first period contains two elements which are hydrogen and helium.