1. Number of Protons:

* Increases: As you move from left to right across a row (period) on the periodic table, the number of protons in the atom's nucleus increases. This is the defining characteristic of moving across a period.

2. Chemical Reactivity (Metals):

* Decreases: Generally, the chemical reactivity of metals decreases as you move from left to right across a period. This is because:

* Electronegativity increases: Metals tend to lose electrons to form positive ions. As you move rightward, elements become more electronegative (they attract electrons more strongly), making them less likely to lose electrons and become less reactive.

* Ionization energy increases: It takes more energy to remove an electron from an atom as you move across a period, making them less likely to participate in reactions.

Important Note: While the general trend for metals is decreasing reactivity, there are some exceptions. For instance, the halogens (Group 17) show an increase in reactivity as you move down the group.

Let me know if you want to explore the trends for nonmetals or other properties!