The Group 1A Elements

In Section 7.13 we saw that the alkali metals all react vigorously with water to release hydrogen gas  

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Lepidolite is mainly composed of lithium, aluminum, silicon, and oxygen, but it also contains significant amounts of rubidium and cesium. 

Several properties of the alkali metals are given in Table 7.8. 

Lithium Siiicate minerais such as spodumene, LiAi(SiA) Eiectroiysis of moiten LiCi 

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The same effects felt by the group 1A elements when a single electron is lost are felt by the group 2A elements when two electrons are lost. For example, loss of two valence-shell electrons from an Mg atom (Is2 2s2 2p6 3s2) gives the Mg2+ cation (Is2 2s2 2p6). The smaller valence shell of the Mg2+ cation and the increase in effective nuclear charge combine to cause a dramatic shrinkage. In the same way, a similar shrinkage is encountered whenever any of the metal atoms on the left-hand two-thirds of the periodic table is converted into a cation. 

Francium Francium, the heaviest of the group 1A elements, is highly radioactive, and no visible amount of the element has ever been prepared. Little is known about its properties from direct observation, but its behavior would presumably be similar to that of the other alkali metals. 

Alkali metal(s) The group 1A elements of the periodic table. 

Note that the use of a Roman numeral in a systematic name is required only in cases in which more than one ionic compound forms between a given pair of elements. This case most commonly occurs for compounds containing transition metals, which often form more than one cation. Elements that form only one cation do not need to be identified by a Roman numeral. Common metals that do not require Roman numerals are the Group 1A elements, which form only 1+ ions the Group 2A elements, which form only 2+ ions and aluminum, which forms only Al3+. Common transition metals that do not require a Roman numeral (because they form only one ion) are zinc (Zn2+) and silver (Ag+). 

All the hydroxides of the Group 1A elements (LiOH, NaOH, KOH, RbOH, and CsOH) are strong bases, but only NaOH and KOH are common laboratory reagents because the lithium, rubidium, and cesium compounds are expensive. The alkaline earth (Group 2A) hydroxides—Ca(OH)2, Ba(OH)2, and Sr(OH)2—are also strong bases. For these compounds 2 moles of hydroxide ion is produced for every 1 mole of metal hydroxide dissolved in aqueous solution. 

Recall that the chemical property most characteristic of a metal is the ability to lose its valence electrons. The Group 1A elements are very reactive. They have low ionization energies and react readily with nonmetals to form ionic solids. A typical example involves the reaction of sodium with chlorine to form sodium chloride,... 

A substance is considered soluble if more than three grams of the substance dissolves in 100 ml of water. The more common rules are listed below. 1. All common salts of the group 1A elements and ammonium ions are soluble. 2. All common acetates and nitrates are soluble. 3. All binary compounds of group 7A elements (other than F) with metals are soluble except those of silver, mercury(l), and lead. 4. All sulfates are soluble except those of barium, strontium, lead, calcium, silver, and mercury(l). 5. Except for those in Rule 1, carbonates, hydroxides, oxides, sulfides, and phosphates are insoluble. ... 

Since ionization energies decrease going down a colunrn in the periodic table, francium should have the lowest first ionization energy of all the alkali metals. As a result, Fr should be the most reactive of all the Group 1A elements toward water and oxygen. The reaction with oxygen would probably be similar to that of K, Rb, or Cs. 

Figure 8.14 The Group 1A elements the alkali metals. Francium (not shown) Is radioactive.

Figure 12.3 shows the alkali metals superimposed on the network of interconnected ideas as we left it at the end of the last chapter. Table 12.1 shows a number of the properties of the Group 1A elements. A quick reference to the table shows that these elements illustrate many classic and expected variations in periodic properties. 

The group 1A elements, called the alkali metals, are all reactive metals. A marblesized piece of sodium explodes violently when dropped into water. Lithium, potassium, and rubidium are also alkali metals. 

Figure 7.14 shows samples of the Group 1A elements. These elements all have low ionization energies, making it easy for them to become ions. In fact, these metals are so reactive that they... 

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