Francium (Fr) has the highest atomic radius in the periodic table. It belongs to the alkali metals group. Its atomic number is 87. The periodic trend of atomic radius suggests that the atomic radius usually decreases along a period (left to right) and increases down a group (top to bottom).

1. The credit for developing the cholera vaccine in 1885 goes to Spanish-French bacteriologist and hygienist Jaime Ferrán.

2. He tested a live attenuated bacterial vaccine during a cholera epidemic in Valencia.

3. Jaime Ferrán's vaccine successfully protected people from cholera and began to be used in vaccination programs around the world.