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Chap. 4-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: 1. Monatomic cations with charges greater than +3 are very rare 2. Electrons from the highest n quantum number are lost first. This is important in determining the cations formed by transition metals. 3. 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.-Group 3A 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 2 6p 1 . Both valence sublevels are in the same level, so the one with the highest l 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 ion.-Group 4A metals, +4 monatomic ions do not exist, so the Group 4A metals cannot lose 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 l quantum number, the outermost p sublevel, to form +2 ions.-Transition Metals 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 3+ (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 +2 ion. Anions formed by non-metals:-Nonmetals form anions by gaining the number of electrons required to fill their p sublevel-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.... View Full Document

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