How did Dmitri Mendeleev develop the first periodic table of the elements?

• A. He classified the elements based on their physical states at room temperature.
• B. He arranged the elements in order of increasing atomic mass and grouped them by similar chemical properties.
• C. He organized the elements alphabetically by their names.
• D. He grouped the elements according to their discovery dates.

Answer: (B)

Verified step by step guidance

1. Understand that Dmitri Mendeleev's key contribution was to arrange elements in a systematic way that revealed patterns in their properties.
2. Recognize that Mendeleev organized the elements primarily by increasing atomic mass, which was the best available measure at his time.
3. Note that he grouped elements with similar chemical properties into columns, creating families of elements with shared characteristics.
4. Appreciate that Mendeleev left gaps in his table where no known element fit the pattern, predicting the existence and properties of undiscovered elements.
5. Conclude that Mendeleev's periodic table was revolutionary because it combined atomic mass order with chemical property grouping, rather than using physical state, alphabetical order, or discovery date.