Question

In the long form of periodic table, elements are arranged in the increasing order of:
(A) Atomic mass
(B) Atomic number
(C) Mass number
(D) Metallic character

Answer 1

Hint: Elements in the long form of the periodic table are arranged on the basis of the fundamental properties that characterizes each of the elements i.e., the number of protons present within an atom’s nucleus.

Complete step-by-step solution:
Elements are arranged in the periodic table from left to right and top to bottom in the increasing order of atomic number.
Earlier, Dimitri Mendeleev arranged the elements according to their atomic mass. Later on, an English physicist, Henry Moseley provided atomic numbers, based on the number of electrons and protons in an atom and modified the periodic table.
According to him, similar properties occur periodically when elements are arranged according to the increasing atomic number. This reduces the length of the periodic table as the isotopes are no longer mentioned. Electronic configuration of any element can be easily traced as the atomic number is the same as the number of electrons present. Atomic numbers also help to understand the trends of each row and period by telling us atomic size. Also, it becomes easy to differentiate between metals and non-metals on the basis of oxidation state obtained by their electronic configuration. These are some of the benefits of arranging elements in order of their atomic number.
This led to more accurate organisation of the periodic table.

Hence, the correct answer is (B).

Note: The atomic number represents the number of protons in the nucleus of an atom which is the identity of an element. Therefore, we can also say that elements in the long form of periodic table are arranged in the increasing order of the number of protons.