Why does the fifth period of the modern periodic table contain 18 electrons?

Correct option is  B) 6th

Elements present in the first period i.e., H and He contain only one shell which is also their valence shell and can accommodate maximum two electrons. As first shell can accommodate only...

Hydrogen (H) : 1s2, Helium (He) : 2s2 Since helium has a complete duplet i.e., two electrons in its valence shell, it has the stable complete electronic configuration.

i. Filling of electrons in the second period: In the second period, electrons are filled in the second shell i.e., n = 2. This shell can accommodate a maximum of eight electrons...

The fourth period corresponds to the filling of fourth shell, n = 4. Therefore, it begins with filling of 4s subshell. The first two elements of the fourth period are K...

A period begins by filling of one electron to the ‘s’ subshell of a new shell and ends when an element corresponding to the same shell attains complete octet (or...

i. First period  ii. f-Block

Nonmetals present in group 17 (halogen family) and group 16 (chalcogens) have highly negative electron gain enthalpies. As a result, they readily accept one or two electrons and form anions (X– or X2–) that...

The Modern periodic table removed various anomalies of Mendeleev’s periodic table as follows:  i. All isotopes of the same element have different atomic masses but same atomic number. Therefore, they occupy...