Question

1. dmitri mendeleev studied the chemical characteristics of elements in the 1800s. he discovered that elements could be arranged in a table according to patterns that occur in their characteristics. which of these processes would be very difficult now without mendeleevs discoveries? predicting the reactivity of elements measuring the atomic mass of elements identifying the color of elements using the chemical symbols of elements

Explanation:

Mendeleev's periodic table organizes elements based on their properties. Predicting reactivity relies on periodic trends (e.g., groups have similar reactivity). Atomic mass measurement was already possible before Mendeleev. Element color identification and using chemical symbols aren't dependent on Mendeleev's table structure for discovery difficulty.

Answer:

Predicting the reactivity of elements.