How do you tell how reactive an element is on the periodic table

hmm For metals, reactivity increases down a group and from right to left across a period. Nonmetals do the opposite. For nonmetals, reactivity increases up a group and from left to right across a period. Francium is the most reactive metal, and fluorine is the most nonmetal.

i believe it is-

d.) gravity pulled particles of dust and gas together to form planets.

periodic trends is an atom that gets larger as the number of electronic shells increase, the radius of atoms increases as you go down a certain group in the periodic table of elements. in general, the size of an atom will decrease as you move from left to right of a certain period.