Question

1. how can scientists predict how an element will react?
2. why was mendeleevs periodic table considered brilliant?
3. how did the discovery of new elements support mendeleevs predictions?
4. describe how the periodic table helps scientists organize and understand elements?

Explanation:

1. Scientists can predict an element's reactivity by looking at its position in the periodic table, valence - electron configuration, and trends in electronegativity, ionization energy, etc.
2. Mendeleev's periodic table was brilliant because he left gaps for undiscovered elements and accurately predicted their properties based on the periodic trends he observed.
3. The discovery of new elements supported Mendeleev's predictions as these new elements fit into the gaps he left in his periodic table and had the properties he predicted.
4. The periodic table helps scientists organize elements by atomic number, and understand trends in properties such as atomic radius, electronegativity, and reactivity across periods and groups.

Answer:

1. By examining its position in the periodic table and electron - related properties.
2. For predicting undiscovered elements and their properties.
3. New elements fit into the predicted gaps with expected properties.
4. Organizes by atomic number and reveals property trends.