How is the modern periodic table organized?

• A. By increasing atomic mass
• B. By increasing atomic number
• C. By alphabetical order of element names
• D. By the order of element discovery

Answer: (B)

Verified step by step guidance

1. Understand that the modern periodic table is arranged based on a fundamental property of elements called the atomic number, which is the number of protons in an atom's nucleus.
2. Recall that earlier versions of the periodic table were organized by increasing atomic mass, but this caused inconsistencies in element properties and groupings.
3. Recognize that arranging elements by increasing atomic number resolves these inconsistencies because the atomic number uniquely identifies each element and reflects its chemical behavior.
4. Note that the periodic table groups elements with similar chemical properties into columns called groups or families, which arise naturally when elements are ordered by atomic number.
5. Conclude that the modern periodic table is organized by increasing atomic number, not by atomic mass, alphabetical order, or discovery order.