The following variations of properties within periods and groups are observed:
(1) Variation of metallic character,
(2) Variation in atomic size,
(3) Variation in ionic radii,
(4) Variation in ionization potentials,
(5) Variation in electron affinities,
(6) Variation in electro negativities,
(7) Variation in stability of oxidation states,
(8) Variation in oxidizing and reducing powers,
(9) Variation in basic properties,
(10) Variation in physical properties.
Some outlines involving variations of properties
q Metallic character is a rough and qualitative combination of (i) electrical and thermal conductivity, (ii) metallic luster (brightness) and (iii) reducing properties,
q (a) As the size increases, valence electron are readily lost, elements become more metallic, because valence electrons are held less strongly due to the increasing size of the atom; (b) As the size decreases, valence electron are less readily lost, elements become less metallic, because valence electrons are held more strongly due to the decreasing size of the atom.
q The greater the nuclear charge, the smaller is the ionic radius in a series (Na+, mg+2, Al+3, Si+4).
q Metals generally have small ionization energy; nonmetals have large values.
q Metals have small electron affinity, nonmetals have large values [good oxidizing agents].
q Higher oxidation states become more stable near the bottom of each transition metal.
Reasons of Variations
(b) the nuclear charge and the number of electrons surrounding the nucleus,
(ii) the total number of electrons, particularly the valence electrons,
(iii) the size of the atoms, i.e. the volume occupied by the electron in various
energy levels.