Beryllium aluminum diagonal relationship

The oxides of metalloids and some of the less electropositive elements are amphoteric (react with both acids and bases). Aluminum oxide, for instance, reacts with acids and with alkalis (aqueous solutions of strong bases). The oxides reveal a strong diagonal relationship between beryllium and aluminum, because beryllium oxide is also amphoteric. 

Aluminum and beryllium have a diagonal relationship. Compare the chemical equations for the reaction of aluminum with aqueous sodium hydroxide to that of beryllium with aqueous sodium hydroxide. 

The diagonal band of metalloids dividing the metals from the non-metals is one example of a diagonal relationship (Section B). So is the chemical similarity of lithium and magnesium and of beryllium and aluminum. For example, both lithium and magnesium react directly with nitrogen to form nitrides. Like aluminum, beryllium reacts with both acids and bases. We shall see many examples of this diagonal similarity when we look at the elements in detail (in Chapters 14 and 15). 

This is another example of the diagonal relationship between beryllium and aluminum. 

As well as the obvious horizontal and vertical trends found in a periodic table, there is also a diagonal relationship between certain sets of elements (lithium and magnesium, beryllium and aluminum, boron and silicon). The diagonal relationship relates an atom to another one that is one over, and one down from it. The effect of Fajans rule means that pairs of atoms are found to have similar size and electronegativity, and this leads to similarities in reactivities and other properties. 

In the middle of the table, triads are grouped horizontally. Three columns are labeled group VIllA because of the horizontal relationships. An example of a horizontal triad is iron, cobalt, and nickel. Sometimes there are also diagonal relationships. For example, beryllium is more. similar to aluminum than it is to magnesium. 

The diagonal relationship between beryllium and aluminum, discussed previously in Chapter 21, is evident in Table 22.1. Both beryllium (in group 2) and aluminum (in group 13) form network covalent solids with fluorine. 

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