Question

how were the elements in the first periodic table arranged?

a. in order of atomic mass

b. in order of date of discovery

c. in order of atomic number

d. alphabetically by element name

Explanation:

The first periodic table, created by Dmitri Mendeleev, arranged elements in order of their atomic mass. Later, the modern periodic table arranges elements by atomic number, but the first one used atomic mass. Options B (date of discovery), D (alphabetically), and the modern basis of atomic number (option C) do not apply to the first periodic table's arrangement.

Answer:

A. In order of atomic mass