How are elements organized in the periodic table?

• A. By increasing atomic mass only
• B. By increasing atomic number
• C. By their chemical reactivity
• D. By alphabetical order of element names

Answer: (B)

Verified step by step guidance

1. Understand that the periodic table is a systematic arrangement of elements based on their properties.
2. Recall that early versions of the periodic table were organized by increasing atomic mass, but this caused inconsistencies in element placement.
3. Recognize that the modern periodic table is organized by increasing atomic number, which is the number of protons in an atom's nucleus.
4. Know that organizing by atomic number aligns elements with similar chemical properties into columns called groups or families.
5. Conclude that the correct organization principle is by increasing atomic number, not by atomic mass, chemical reactivity, or alphabetical order.