Question

1. in the modern periodic table, elements are arranged according to a. decreasing atomic mass. b. increasing atomic number. c. mendeleevs original design. d. the date of their discovery.

Explanation:

In the modern Periodic Table, elements are arranged in order of increasing atomic number. This is the fundamental organizing principle of the modern - day Periodic Table. Atomic mass was the basis in Mendeleev's original design, but it has been replaced by atomic number. The date of discovery is not a factor in the arrangement of elements in the Periodic Table.

Answer:

There is no option indicating increasing atomic number among the given choices. But if we were to correct the options and choose the correct one, it should be "increasing atomic number". As for the given options, none of them (a. decreasing atomic mass, b. increasing atomic number - not present as an option here, c. Mendeleev's original design, d. the date of their discovery) is correct according to the modern - day arrangement principle.