-Cations are produced by the loss of the valence electrons with the highest n quantum
number. Consequently, first row transition metals lose their 4s electrons before they lose
any 3d electrons.
-Metals are characterized by low ionization energies, so they lose electrons to become
cations. The charge on the cation is determined by the number of electrons that are lost.
Some metals lose all of their valence electron, but others lose only some of their valence
electrons. The following rules help determine which electrons are lost:
Monatomic cations with charges greater than +3 are very rare
Electrons from the highest n quantum number are lost first. This is important in
determining the cations formed by transition metals.
Electrons from the highest l quantum number are lost first within a shell. This is
important for the heavier metals in Groups 3, 4, and 5.
Cations formed by metals:
-Group 1A and 2A
metals lose their electrons and become +1 and +2 respectively.
metals lose all of their valence electrons to form +3 ions. Tl forms both +3
and +1 ions but not a +2 ion. The reason is that the heavier main group elements can lose
only a portion of their valence shell. Tl is 6s
. Both valence sublevels are in the same
level, so the one with the highest
quantum number is emptied first. Thus, Tl can lose the
6p and not the 6s to form the +1 ion, but it cannot lose the 6s and not the 6p to form a +2
metals, +4 monatomic ions do not exist, so the
Group 4A metals
all of their valence electrons. However, the heavier metals in the group (Sn and Pb) can
lose the electrons in the sublevel with the highest
quantum number, the outermost p
sublevel, to form +2 ions.
lose electrons in the level with the highest n quantum number. Thus,
most transition elements form +2 ions. Scandium is an exception because it loses all three
valence electrons to form Sc
(no +2 ion). Silver forms only a +1 ion and copper forms
both +2 and +1 ions. In addition, several transition metals form a +3 ion in addition to a
Anions formed by non-metals:
-Nonmetals form anions by gaining the number of electrons required to fill their p
-Nonmetals are electronegative, so they tend to gain electrons to become anions. The
number of electrons gained equals the number required to fill their valence shell. A filled
valence shell for a nonmetal contains eight electrons (two s and six p electrons).
-charge on an anion = group number - eight
Group 7A gains an electron to be -1, Group 6A becomes -2, Group 5A becomes -3
Monatomic anions with charges of -4 do not exist, so the Group 4A nonmetals do
not form anions.
-A cation is smaller than its atom, while an anion is larger than its atom.
-The size of an ion is determined by the n quantum number of the outermost electrons
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