On the modern Periodic Table, the elements are arranged in order of increasing (1) atomic mass (3) mass number (2) atomic number (4) oxidation number

On the modern Periodic Table, the elements are arranged in order of increasing(1) atomic mass

They are arranged in order of increasing atomic number. So the answer is definitely 2). I say this because all the elements in the periodic table follow each other based on their atomic number. To prove this, hydrogen has an atomic number of 1, and it is followed by helium which has an atomic number of 2. Lithium is next, and it has an atomic number of 3. As you can see, i am very sure the answer is 2. Hope i helped. Have a nice day.