Which element in the periodic table has the largest atomic radius?
The atomic radii of the main group elements increase going down a group and decrease going across a period. In other words, the lower left corner of the periodic table has the largest atomic radii and the upper right has the smallest. Going from the top to the bottom of a group increases the radius due to the electrons filling orbitals that are successively farther away from the nucleus (increasing principle quantum number n.) Going from left to right across a period decreases the radius due to the addition of a proton to each successive nucleus. An electron is also added, but the increased attraction of the nucleus to the electron cloud is stronger than the increased repulsion between the electrons. The electron cloud therefore shrinks in closer to the nucleus. There is a jump in the atomic radius from a noble gas atom to the following alkali metal atom. This is because the electrons start occupying the next energy level. Lawrencium has the largest atomic radius. Lawrencium (Unniltriu