Question

Tell whether each statement about ions is true or false. If a statement is false, explain why. (a) A cation is formed by addition of one or more electrons to an atom. (b) Group \(4 \mathrm{~A}\) elements tend to lose four electrons to yield ions with a +4 charge. (c) Group 4A elements tend to gain four electrons to yield ions with a -4 charge. (d) The individual atoms in a polyatomic ion are held together by covalent bonds.

Short answer

(a) False, cations form by losing electrons. (b) False, Group 4A doesn't lose 4 electrons. (c) False, Group 4A doesn't gain 4 electrons. (d) True, held by covalent bonds.

Step-by-step solution

Analyze the Statement about Cations

A cation is formed by the removal of one or more electrons from an atom, not by the addition of electrons. By removing electrons, the atom becomes positively charged because it now has more protons than electrons. Hence, statement (a) is false.

Evaluate Group 4A Elements and Electrons

Group 4A elements typically do not lose four electrons to form a +4 charge. They are more likely to form covalent bonds by sharing electrons rather than losing four electrons, as this requires a lot of energy. Therefore, statement (b) is false.

Examine the Electron Gain for Group 4A

Group 4A elements also do not tend to gain four electrons to form a -4 charge. Similar to losing electrons, gaining four electrons is uncommon and energetically unfavorable. They are more inclined to participate in covalent bonding. Hence, statement (c) is false.

Understand Polyatomic Ions and Bonding

In a polyatomic ion, the atoms are indeed held together by covalent bonds. These ions are composed of multiple atoms bonded covalently, acting as a single charged unit. Statement (d) is true.

Key concepts

Cations and Anions

Ions are charged particles resulting from the gain or loss of electrons in atoms. When atoms lose electrons, they become positively charged and are known as cations. This occurs because there are more protons (which are positively charged) than electrons in the atom. On the other hand, when atoms gain electrons, they acquire a negative charge and are called anions. Here, the number of electrons exceeds the number of protons. As a simple rule, cations are formed by electron removal, and anions are formed by electron addition.

• Cation: Formed by losing electrons -> Positive Charge
• Anion: Formed by gaining electrons -> Negative Charge

Understanding these concepts is crucial as they help in predicting the behavior of elements in chemical reactions and how they form bonds.

Group 4A Elements

Group 4A elements, located in the carbon family of the periodic table, have four valence electrons. Rather than losing all four or gaining four additional electrons (which would be energetically unreasonable), these elements typically engage in forming covalent bonds. While they have the potential to form both positive and negative ions theoretically, in practice, these elements do not easily form ions with a +4 or -4 charge.

• Group 4A includes carbon, silicon, germanium, tin, and lead.
• They often share electrons to complete their valence shell.

This sharing of electrons is a more stable and energy-efficient approach for these elements, underpinning significant chemical structures, especially in organic chemistry.

Electron Transfer

Electron transfer is fundamental to the formation of ions and the driving force behind chemical bonding. In ionic compounds, one atom donates electrons, becoming a cation, while another atom accepts electrons, becoming an anion. This exchange stabilizes the participating atoms, adhering to the principle of achieving a complete valence shell, similar to noble gases.
However, not all elements prefer this process. For Group 4A elements, complete loss or gain of four electrons is uncommon due to the high energy requirement. Instead, they often utilize covalent bonding as a means of stabilizing their electron configuration, thus circumventing the energetically costly process of full electron transfer.

Covalent Bonding

Covalent bonding is a common method by which atoms achieve stability. It involves the sharing of one or more pairs of electrons between atoms, allowing them to fill their outer electron shells effectively. This type of bonding principally occurs among nonmetals, which have similar electronegativities.
In the case of polyatomic ions, groups of atoms are held together by covalent bonds, even when the group carries an overall charge. These ions function as single charged entities in chemical reactions, illustrating the dual nature of covalent bonding and ionic interaction within compounds.

• Occurs between nonmetals with similar electronegativities.
• Results in the formation of molecules or compounds.
• Key for forming polyatomic ions which have both covalent bonds and charge.

Covalent bonds are essential to the structure and function of many biological molecules, such as DNA, proteins, and carbohydrates.