Question

(a) Without referring to Figure 4.10 , give the oxidation numbers of the alkali and alkaline earth metals in their compounds. (b) Give the highest oxidation numbers that the Groups \(3 \mathrm{~A}-7 \mathrm{~A}\) elements can have.

Short answer

For part (a), alkali metals have an oxidation state of +1 and alkaline earth metals have an oxidation state of +2 in their compounds. For part (b), elements in groups 3A - 7A can have maximum oxidation numbers equal to their group number, i.e., +3 to +7 respectively.

Step-by-step solution

Identify Alkali and Alkaline Earth Metals

The alkali metals consist of elements in Group 1 of the periodic table: lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), and francium (Fr). The alkaline earth metals are in Group 2, and are beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra).

Alkali and Alkaline Earth Metals Oxidation State

Alkali metals (Group 1) always have an oxidation state of +1 in their compounds. Alkaline earth metals (Group 2) have an oxidation state of +2 in their compounds.

Identify Groups 3A - 7A Elements

Groups 3A - 7A on the periodic table contain the elements of the p block (other than the noble gases). Group 3A has elements like boron (B), aluminum (Al), gallium (Ga), indium (In), and thallium (Tl). And so on until group 7A with elements like fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At).

Oxidation States for Groups 3A - 7A Elements

Generally, these groups of elements can have a maximum oxidation state equal to the group number. So for group 3A, the maximum oxidation state is +3, for group 4A it's +4, and so on until group 7A, where the maximum oxidation number is +7.

Key concepts

Alkali Metals Oxidation State

Understanding the oxidation state of alkali metals is a crucial foundation for mastering chemistry concepts. Alkali metals, which include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), and francium (Fr), belong to Group 1 of the periodic table. Each of these metals has a characteristic oxidation state of +1 when they form compounds. This oxidation state is due to the fact that alkali metals have a single electron in their outermost shell, which they readily lose in order to achieve a stable noble gas electron configuration. The loss of this single electron forms a cation with a +1 charge, reflecting their +1 oxidation state.

This uniformity among the alkali metals makes predicting their chemical behavior relatively straightforward in this regard. For example, when sodium reacts with chlorine to form sodium chloride, the sodium atom loses one electron to become a sodium ion with a +1 oxidation state.

Alkaline Earth Metals Oxidation State

Moving on to Group 2 of the periodic table, we find the alkaline earth metals which include beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). These metals consistently show an oxidation state of +2 in their compounds. The reason behind this is their electronic configuration, which includes two electrons in their outer shell. By losing these two electrons, they form a divalent cation with a +2 charge, and thus, their oxidation state in compounds is +2.

Take calcium, for instance; when it reacts with oxygen, it forms calcium oxide with calcium ions having a +2 oxidation state. This characteristic is significant since it affects the properties of the compounds they form, making them distinct from those formed by alkali metals.

P Block Elements Oxidation State

The p block elements span Groups 3A to 7A on the periodic table and display a diverse range of oxidation states. Their oxidation states generally reflect their group number; this means that the maximum oxidation state an element from one of these groups can exhibit is typically equal to the group number. For example, nitrogen (Group 5A) can have an oxidation state as high as +5. However, it is important to note that the actual oxidation state can vary depending on the specific compounds and reaction conditions.

P block elements can sometimes exhibit multiple oxidation states because of the availability of d and p orbitals where the electrons can reside. Elements like sulfur can have +4 in sulfite ions (SO3^2-) or +6 in sulfate ions (SO4^2-). This flexibility makes the chemistry of p block elements particularly rich and varied, and it plays a critical role in the reactivity and types of compounds that these elements can form.

Periodic Table Groups

The periodic table is organized into groups that are vertical columns numbering from 1 to 18. Group numbers are essential because they can often predict the oxidation states that elements are most likely to assume. For element groups in the s block (Groups 1 and 2), which include alkali and alkaline earth metals, the group number corresponds to the oxidation state as previously discussed—the +1 for alkali metals and +2 for alkaline earth metals.

As we move into the p block (Groups 3A to 7A), the maximum oxidation state of an element generally corresponds to its group number. However, the transition metals in the d block exhibit a variety of oxidation states, making their chemistry more complex. Understanding the typical oxidation states of the elements in their respective groups can be an invaluable tool when predicting the formulas of compounds and the outcomes of chemical reactions.