in the third period as the atomic number increases from group 1 to group 18 the atomic radius increases by 6.
in the third period as the atomic number increases from group 1 to group 18 the atomic radius increases by 6.
in the third period as the atomic number increases from group 1 to group 18 the atomic radius?
6
atomic radii vary in a predictable and explicable manner across the periodic table. for instance, the radii generally decrease along each period (row) of the table, from the alkali metals to the noble gases; and increase down each group (column). the radius increases sharply between the noble gas at the end of each period and the alkali metal at the beginning of the next period. these trends of the atomic radii (and of various other chemical and physical properties of the elements) can be explained by the electron shell theory of the atom; they provided important evidence for the development and confirmation of quantum theory. the atomic radii decrease across the periodic table because as the atomic number increases, the number of protons increases across the period, but the extra electrons are only added to the same quantum shell. therefore, the effective nuclear charge towards the outermost electrons increases, drawing the outermost electrons closer. as a result, the electron cloud contracts and the atomic radius decreases.
atomic radius
the way the atomic radius varies with increasing atomic number can be explained by the arrangement of electrons in shells of fixed capacity. the shells are generally filled in order of increasing radius, since the negatively charged electrons are attracted by the positively charged protons in the nucleus. as the atomic number increases along each row of the periodic table, the additional electrons go into the same outermost shell; whose radius gradually contracts, due to the increasing nuclear charge. in a noble gas, the outermost shell is completely filled; therefore, the additional electron of next alkali metal will go into the next outer shell, accounting for the sudden increase in the atomic radius.
atomic radius