How many electrons are there in the L-shell of Boron?

What is the atomic number of the element unniloctium?

The Lanthanoid series is the same as the Actinoid series.

O2-, F–, Na+ and Mg2+ are called as ______

The period’s number corresponds to the highest _____

X(g) → X+(g) + e–. What does this chemical reaction need to occur?

In Mendeleev’s periodic classification, what is the number of groups?

Metals consist of __% of the elements known.