definition of atomic radius
a measure of the size of an atom
half the distance between the two nuclei of two covalently bonded atoms
atomic radii trend across a Period
decrease
atomic radii trend down a Group
increase
explanation of atomic radii trends
Electron shell theory
why does atomic radii decrease across a period
increased positive nuclear charge, greater pull of electrons
why does atomic radii increase down a group
increased number off shells, increasing shielding from nucleus, weaker pull of nucleus
atomic radii increases sharply between
the noble gas at the end of one period and the alkali metal of the next period
explanation for sharp increase between noble gas and alkali metal
alkali metals have one extra principle quantum shell, increased shielding
definition of ionic radii
a measure of the size of an ion
ionic radii increase with
increasing negative charge
ionic radii decrease with
increasing positive charge
formation of negative ions
accepting extra electrons only
which electrons are held weakly to the nucleus
the outermost electrons
the larger the ionic radius, the
greater the negative charge
formation of positive ions
losing electrons only
the smaller the ionic radius, the
greater the positive charge