Question

What determines the properties of elements?
(A) The number of electron shells
(B) The number of electrons that fill the outer shell
(C) The total number of electrons
(D) The average atomic mass
(E) The number of neutrons

Answer 1

Hint: Electrons are the most fundamental subatomic particles present in almost every element around us. Elements undergo different types of chemical changes depending upon the number of electrons present in their outermost region that will take part in reaction.

Complete answer:
An element is a pure substance that cannot be broken down into a simpler form. Each element possesses a unique set of electrons.
Chemical properties of each element are determined by the element’s electron configuration, and particularly by the number of electrons present in its outermost shell. The electrons that are present in the outermost shell of an atom are known as valence electrons.
The chemical reactions between different elements take place due to the interactions between their valence electrons. The number and location of these electrons decide what type of change the element will undergo. In proper words we can say that the properties of elements are determined by the number of electrons present in the outermost shell.
An element’s location in the periodic table is also largely dependent on the number of valence electrons it possesses. The number of valence shell electrons determines the group number of the element, and the orbital in which the valence electrons are situated determines the element’s block name (s, p, d or f). The periodic table uses all this information to group elements according to their physical and chemical properties. It has become an extremely useful tool for assessing elemental and chemical trends.

Hence the correct answer is (B) The number of electrons that fill the outer shell.

Note:
Valence electrons categorize elements into different types such as metals are the elements that can easily lose electrons to form cations while the non-metals tend to gain electrons to form anions.