Question

9 which criterion is primarily used in the modern periodic table, and what distinguishes it from the one used by mendeleev? a atomic mass, which prioritizes similar chemical properties b chemical reactivity, focusing on element similarities c atomic number, representing the number of protons in the nucleus d atomic volume, used to predict element properties

Explanation:

The modern periodic table arranges elements based on atomic number (number of protons). Mendeleev's table was based on atomic mass. Atomic - number - based arrangement better explains periodic trends and properties.

Answer:

C. Atomic number, representing the number of protons in the nucleus