generally the atomic radius decreases across a period from left to right and increases down a given group elements atomic radii and the periodic table atomic size periodic table 2 svg atomic radius trends in the periodic table periodictabledraft15 gif ionization energy is the energy need to completely remove an electron from an atom ionization energy increases going up and to the right periodic table trends 1 after collecting large amounts of data generally accepted atomic radii are known for most elements in the periodic table atomic radii determine this way periodic table what are the atomic radius trends what causes them notice the general trend is for the ionization energy to increase going across a period this makes sense if we recall the atomic radius decreases going as we go from left to right in the periodic table we see a large increase in atomic radius as we reach each new 1a element li na k rb cs fr periodic table trends what happens to the atomic radii as you go across from li to ne periodic trends atomic radius atomic radius trend atomic radius definition formula example the sizes of cations and anions follow similar trends to those of neutral atoms in general anions are larger than the corresponding neutral atom atomic and ionic radii trends among groups and periods of the periodic table kbc lo 30 item 4 use the concepts of ettective nuciear charge shielding comparative atomic sizes png periodic trends atomic radii chart periodic trends atomic radius slide 1 periodic trends the peaks correspond with the noble gases at the end of a period and the troughs with the group 1 alkali metals at the start of a period as you go across atomic radius defintion factors affecting trends in periods and groups figure 23 22 variation in atomic radius of transition metals as a function of the periodic table group number effective nuclear charge