![]() Ion Radius Example : Which of the following ions has the largest radius? (1) S, S2-, O2- (2) O2-, Na+, Al3+ Ion Radius cations are always smaller than their parent atoms anions are always larger than their parent atoms +11 – 10 = +1 11Na +19 – 18 = +1 Zeff essentially remains constant 19K +37 – 36 = +1 37Rb However, more main shells are added and principal quantum number of valence electrons increaseĪtomic Radius atomic radius increases atomic radius increases atomic radius increases Increasing Zeff along a period attract valence electrons more strongly, making the atom more compact Fluorine LithiumĪtomic Radius Atomic radii increase with the atomic numbers within a group. Valence electrons are more strongly bound as atomic number increases within a periodĮffective Nuclear Charge Example : Which electron is more tightly bound: 2p electron of Ne or 3s electron of Na? Which electron would be easier to remove?Ītomic Radius Atomic radii decrease with the atomic numbers within a period. +11-10=+1 +12-10=+2 +13-10=+3 +14-10=+4 Zeff increases along a period # of protons increases, but the # of core electrons stay the same along period. + + + + + + + - Effective Nuclear Charge Effective nuclear charge (Zeff) is used to measure how tightly (outer-shell) electrons are bound to nucleus Zeff = # of proton - # of core electrons Valence electrons see nucleus and core electrons as a single unit core Valence electrons experience approximately the total charge of protons and core electrons valence electronsĮffective Nuclear Charge Example : What is the effective charge of 2p electron of N ? Example : What is the effective charge of 4s electron of Ca?Įffective Nuclear Charge Effective charge, Zeff, increases with the atomic numbers within a period. Periodic Table and Electron Configurations reactivity) of atoms depends on… Number of electrons Electron configuration How tightly electrons are bound to nucleus Periodic Table Halogen Alkaline earth metal Transition metals Alkali metal rare gas ![]() Mendelejeff, Zeitscrift für Chemie12, 405-406 (1869) In the modern version, elements are ordered according to atomic number Dimitri Mendeleev (1834-1907) Elements within a same vertical group have similar properties Mendeleev ordered known elements according to their weight D. ![]()
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