Question

How did the work of Dmitri Mendeleev differ from that of John Newlands in the development of the periodic table?
Mendeleev arranged the elements according to increasing atomic mass.
Mendeleev predicted elements that would later be discovered.
Mendeleev identified elements that had similar properties.
Mendeleev organized elements into triads based on their properties.

Answer 1

Correct answers: 1, 2 and 3 are true descriptions of Mendeleev’s work; 4 is false.

Brief explanation of the difference from Newlands:
- Both Newlands and Mendeleev ordered elements roughly by increasing atomic mass (so statement 1 is true for Mendeleev but not a key difference).
- Mendeleev differed crucially by arranging elements into vertical groups (families) of similar properties more systematically (statement 3) and by leaving gaps for undiscovered elements, predicting their existence and properties (statement 2). Newlands proposed the “law of octaves” (repeating every eight elements) and did not leave gaps or predict new elements, which led to incorrect placements and less acceptance.
- Statement 4 is incorrect: the “triads” idea belonged to Döbereiner; Mendeleev organized a periodic table of groups and periods, not triads.