Monatomic ions aluminum

The oxidation number of an element in a monatomic ion is equal to the charge of that ion. In the ionic compound NaCl, sodium has an oxidation number of +1, chlorine an oxidation number of — 1. The oxidation numbers of aluminum and oxygen in A1203 (Al3+, O2- ions) are +3 and —2, respectively. 

Similarly, the formula of aluminium chloride is AICI3 because the aluminum atom has 3 valence electrons that it can donate to form the 3+ ion. Charges on the most common monatomic ions are presented in Figure 5.11. 

Suppose your instructor asked you to write the proper chemical formula for aluminum chloride. The first step is to look up the elemental symbol and the oxidation number of each of the elements involved. Because this compound contains only monatomic ions, we can find both of the required oxidation numbers in the first group of oxidation numbers. 

Write formulas that correspond to the following names for monatomic ions (a) bromide ion, (b) aluminum ion, and (c) gold(l) ion. 

For ions composed of only one atom (that is, monatomic ions) the oxidation number is equal to the charge on the ion. Thus Li+ has an oxidation number of +1 Ba ion, +2 Fe, +3 1 ion, 1 ion, 2 and so on. All alkali metals have an oxidation number of +1 and all alkaline earth metals have an oxidation number of +2 in their compounds. Aluminum has an oxidation number of +3 in all its compounds. 

Across a period. The decrease in metallic behavior across a period is consistent with a decrease in size, an increase in IE, and a more favorable (more negative) EA. Consider Period 3 elements at the left tend to form cations, and those at the right tend to form anions. Sodium and magnesium are metals that occur as Na and Mg - in seawater, minerals, and organisms. Aluminum is a metallic element and occurs as Al + in some compounds, but it bonds covalently in most others. Silicon (Si) is a shiny metalloid that does not occur as a monatomic ion. Phosphorus is a white, waxy nonmetal that occurs rarely as P, whereas crumbly, yellow sulfur forms S in many compounds, and gaseous, yeUow-green chlorine occurs in nature almost always as Cl . 

Most of the main-group metallic elements have one monatomic cation with a charge equal to the group number in the periodic table (the Roman numeral). Example aluminum, in Group III A, has a monatomic ion Al. ... 

As you might expect, this idea also applies to other groups in the periodic table. Group lA/1 elements form monatomic ions by losing one electron per atom, and aluminum, a Group 3A/13 element, loses three electrons per atom. The equations for the ions formed by atoms of the Period 3 elements are ... 

Table 12.1 shows how electrons are gained and lost when nitrogen, oxygen, fluorine, sodium, magnesium, and aluminum form monatomic ions that are isoelectronic with a neon atom. The pattern built around neon is duplicated for other noble gases. Thus, phosphoms, sulfur, chlorine, potassium, calcium, and scandium (Z = 21) are the elements that form ions that are isoelectronic with argon, and five of the elements on either side of krypton form ions that duplicate the electron configuration of krypton. 

FIGURE 6.4 Lewis structures of the sodium, magnesium, and aluminum monatomic ions. 

Monatomic cations are named after the element if there is only one such ion. Example Al " is called aluminum ion Na is called sodium ion. 

A monatomic cation is named simply by adding the word ion to the name of the element. Thus, the ion of potassium, K, is known as potassium ion. Similarly, the cations formed by the elements magnesium and aluminum (Mg " " and AP ) are called magnesium ion and aluminum ion, respectively. It is not necessary for the name to specify the charge on these ions because their charges are equal to their group numbers. 

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