9. Electrons in Atoms and the Periodic Table

In the simplified valence-electron model, what most directly determines the chemical reactivity of an atom?

What is the group number and number of valence electrons for each of the following elements? e. barium

Complete each of the statements a to d using 1, 2, or 3: 1. decreases 2. increases 3. remains the same Going from left to right across Period 4, d. the number of valence electrons