How are elements arranged on the periodic table?

How are elements arranged on the periodic table?

• A. Increasing atomic number
• B. Increasing atomic mass
• C. Increasing number of electrons
• D. Increasing number of protons only

Answer: (A)

Elements are arranged by increasing atomic number—the number of protons in the nucleus. This number uniquely identifies each element and determines the arrangement of electrons in a neutral atom, which in turn drives the repeating chemical properties we see across periods and down groups. Atomic mass can vary because of different numbers of neutrons (isotopes), so using mass would misorder elements and disrupt the predictable trends. So, as you move across the table or down it, you’re adding one proton at a time, keeping the structure consistent with each element’s identity and behavior.

Elements are arranged by increasing atomic number—the number of protons in the nucleus. This number uniquely identifies each element and determines the arrangement of electrons in a neutral atom, which in turn drives the repeating chemical properties we see across periods and down groups. Atomic mass can vary because of different numbers of neutrons (isotopes), so using mass would misorder elements and disrupt the predictable trends. So, as you move across the table or down it, you’re adding one proton at a time, keeping the structure consistent with each element’s identity and behavior.