Question

The family of the least reactive elements is.
A. Alkali metals.
B. Alkaline earth metals.
C. Noble gases.
D. Halogens.
E. Transition metals.

Answer 1

We know that the electrons in the outermost shell are called valence electrons and the number of electrons it accepts or donates to form a bond is called the valency of an electron. We also remember that the chemical activity of a compound or an atom depends on the number of outermost electrons. If the outermost shells are filled then the atom is inert. If the outermost shell is not filled then to fill the outermost shell, it accepts or donates electrons between other atoms.

Complete step by step answer: We know that the noble gases are the least reactive elements because of the filled orbitals. Therefore, option C is correct.
The most reactive elements are the one that has very few electrons in the outermost valence shell so alkali metals and alkaline earth metals are highly reactive.
Therefore, option A and B are incorrect.
Halogens are the most reactive elements because they have higher electronegativity values. After all, it has five electrons in the valence cell. To get stable electronic configuration halogens to need only one electron which makes it highly attracted to the electron.
Therefore, option D is incorrect.
The general valence shell configurations of every transition element are $n{s^2}\left( {n - 1} \right){\text{ }}{d^{1-10}}.$All the d-block elements are classified into four series corresponding to the filled outer shells of orbitals. They are reactive because they have electrons to react. Hence, option E is incorrect.

So, the correct answer is “Option C”.

Note: Now we can see the properties of the noble gases:
-Their outer shell of valence electrons is considered to be full which gives them a little tendency to participate in chemical reactions.
-The melting and boiling points of noble gas are close together which differs by less than which means that they are liquids over only a small temperature range.