Читать книгу Earth Materials онлайн

65 страница из 155

 Column 13 (IIIA) elements such as Al+3 commonly exist as trivalent (+3) cations by losing three electrons (s2, p1).

 Column 14 (IVA) elements such as Si+4 commonly exist as tetravalent (+4) cations by losing four electrons. The behavior of the heavier elements in this group is somewhat more variable than in those groups discussed previously. It depends on the chemical reaction in which the elements are involved. Tin (Sn) and lead (Pb) behave in a similar manner to silicon and germanium in some chemical reactions, but in other reactions they only lose the two s‐electrons in the highest principal quantum level to become divalent cations.

 Column 15 (VA) elements commonly have a wide range of ionization states from tetravalent (+5) cations through trivalent (−3) anions. These elements are not particularly electropositive, nor are they especially electronegative. Their behavior depends on the other elements in the chemical reaction in which they are involved. For example, in some chemical reactions, with electropositive elements, nitrogen attracts three additional electrons to become the trivalent anion N−3. In other chemical reactions, with electronegative elements, nitrogen releases as many as five electrons in the second principal quantum level to become the pentavalent cation N+5. In still other situations, nitrogen gives up or attracts smaller numbers of electrons to form a cation or anion of smaller charge. All the other elements in group VA exhibit analogous situational ionization behaviors. Phosphorous, arsenic, antimony and bismuth all have ionic states that range from +5 to −3.