Which of the following is a key feature of the modern periodic table?

• A. All elements are classified as metals.
• B. The table is organized by alphabetical order of element names.
• C. Elements are arranged in order of increasing atomic number.
• D. Elements are grouped solely by their atomic mass.

Answer: (C)

Verified step by step guidance

1. Understand that the modern periodic table is organized based on a fundamental property of elements, which helps predict their chemical behavior.
2. Recall that earlier versions of the periodic table were arranged by atomic mass, but this led to inconsistencies in element properties.
3. Recognize that the modern periodic table arranges elements in order of increasing atomic number, which is the number of protons in an atom's nucleus.
4. Know that this arrangement groups elements with similar chemical properties into columns called groups or families.
5. Conclude that the key feature of the modern periodic table is that elements are arranged in order of increasing atomic number, not by alphabetical order, atomic mass, or classifying all as metals.