Which elements has the smallest first ionization energy?

Cesium has smallest ionization energy.

Explanation:

Ionization energy is the energy that an atom at ground state must be absorb to release an electron to form a cation. for eg.

H ⇒

The unit of ionization energy is .

The ionization energy is minimum for cesium  & maximum for fluorine.

Ionization energy depends upon the radius of atom. cesium has smallest radius so it has low Ionization energy.

Therefore the cesium has smallest ionization energy.

answer; equivalent to a one(1) horsepower motor;

the skeletons of most mammals reach a certain size and then stop growing. however, many animals, including some mammals, keep growing throughout their lives. kangaroos, for example, just keep growing and growing until they die. also, the longer an animal lives the greater the chance it might catch some deadly disease.