Student Question

What type of bonding you would expect to see between the following pairs of elements?

1. Mg and Ar

2. Ca and S

3. K and K

4. Li and Na

Expert Answers

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Bonding occurs so that atoms can become more stable. In many cases, increased stability is characterized by obtaining eight valence electrons in the atom. Valence electrons are the electrons located in the outermost energy level of the atom. 

Magnesium (Mg) and Argon (Ar)

Argon is a member of the noble gas family of elements. This means that it already has eight valence electrons in its outermost shell. Because of this, Ar rarely bonds with other atoms to form compounds. Therefore, you would not expect a bond to form between Mg and Ar atoms.

Calcium (Ca) and Sulfur (S)

Ca is a metal and sulfur is a nonmetal. When Ca donates its two valence electrons to sulfur, both atoms achieve eight valence electrons and are more stable. When Ca loses electrons, it becomes positively charged. When S gains electrons, it becomes negatively charged. The strong attraction between these postitive and negative charges is called an ionic bond.

Potassium (K) and Potassium (K)

K is a metal. Bonds between identical metals are called metallic bonds. In metallic bonding, the valence electrons of each atom are free to move around between atoms forming a "sea of electrons". The atoms are held together by the strong attraction between the moving electrons and the positively charged nuclei.

Lithium (Li) and Sodium (Na)

Li and Na are both metals and do not form compounds with one another; however, they can form alloys. An alloy is a type of homogeneous mixture. 

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