Which significant change was made to Mendeleev's periodic table to create the modern periodic table?

• A. Elements were grouped according to their physical state (solid, liquid, gas).
• B. Elements were arranged by increasing atomic number instead of atomic mass.
• C. The noble gases were removed from the table.
• D. Metals and nonmetals were placed in separate tables.

Answer: (B)

Verified step by step guidance

1. Understand that Mendeleev's original periodic table arranged elements primarily by increasing atomic mass and grouped elements with similar chemical properties in the same columns.
2. Recognize that the modern periodic table arranges elements by increasing atomic number, which is the number of protons in an atom's nucleus, rather than atomic mass.
3. Note that arranging elements by atomic number resolves inconsistencies in Mendeleev's table where elements did not fit perfectly by atomic mass but had similar chemical properties.
4. Be aware that the inclusion of noble gases as a new group and the placement of metals and nonmetals in the same table are features of the modern periodic table, but these are not the primary change from Mendeleev's table.
5. Conclude that the key significant change from Mendeleev's periodic table to the modern periodic table is the ordering of elements by increasing atomic number instead of atomic mass.