Question

Which of the following explain how an ion is formed? Explain your answer. a. adding or subtracting protons to/from an atom b. adding or subtracting neutrons to/from an atom c. adding or subtracting electrons to/from an atom

Short answer

An ion is formed by adding or subtracting electrons to/from an atom. This is because changing the number of electrons directly impacts the atom's electrical charge, resulting in either a positively charged cation (electron loss) or a negatively charged anion (electron gain). Options a and b, involving changes in protons or neutrons, do not result in ions.

Step-by-step solution

Option a: adding or subtracting protons to/from an atom

Changing the number of protons in an atom would result in a completely different element, as the atomic number (number of protons) defines an element. Therefore, adding or subtracting protons to/from an atom does not form an ion.

Option b: adding or subtracting neutrons to/from an atom

Changing the number of neutrons in an atom results in the formation of isotopes, which are atoms of the same element with different mass numbers due to the varying number of neutrons. Isotopes still have the same charge as the original atom since the number of electrons and protons remains the same. Therefore, adding or subtracting neutrons to/from an atom does not form an ion.

Option c: adding or subtracting electrons to/from an atom

Changing the number of electrons in an atom directly impacts the atom's electrical charge. Losing an electron will result in a positively charged ion, called a cation, and gaining an electron will result in a negatively charged ion, called an anion. This process of adding or subtracting electrons to/from an atom leads to the formation of ions. Based on the analysis above, the correct answer is: c. adding or subtracting electrons to/from an atom

Key concepts

Electron Transfer

Electron transfer is the process responsible for the formation of ions. Ions are atoms or molecules with a net electric charge due to the loss or gain of one or more electrons.
This process is crucial because it allows elements to attain a stable electron configuration, often similar to the nearest noble gas. By transferring electrons, atoms can fulfill the octet rule—having eight electrons in their valence shell, which is a marker of stability.

• If an atom loses electrons, it becomes positively charged, forming a cation.
• If an atom gains electrons, it becomes negatively charged, forming an anion.

This transfer is a foundational concept in chemistry and is essential for the formation of ionic bonds, where cations and anions attract each other to create stable compounds.

Cation

A cation is an ion with a positive charge. This results from an atom losing one or more electrons.
To understand why cations form, it is helpful to consider the concept of electron configuration. Atoms strive to reach a stable electron arrangement. By losing electrons, certain atoms, especially metals, achieve this and stabilize their electronic structures.

• For example, when a sodium atom loses one electron, it becomes a sodium cation \(\text{Na}^+\).
• The loss of an electron takes it closer to a stable electronic state similar to the noble gases.

Cations often participate in forming ionic compounds by bonding with anions, balancing the charge to create neutral compounds.

Anion

An anion is an ion with a negative charge formed when an atom gains one or more electrons.
Atoms, particularly nonmetals, gain electrons to reach a complete valence shell, achieving stability akin to noble gases.

• Consider the chloride ion \(\text{Cl}^-\), formed when a chlorine atom gains an electron.
• This gain of electron brings chlorine to a stable configuration similar to argon.

Anions are key participants in forming ionic bonds, where they pair up with cations. This pairing enables the creation of a full, stable electron configuration for both ions involved.

Atomic Structure

The atomic structure comprises the nucleus and the electron cloud surrounding it. The nucleus contains protons and neutrons, while electrons orbit this nucleus in various shells or levels.
The number of protons, which defines the atomic number, determines the element. Any change in this number results in a different element. Neutrons affect the mass and form isotopes but do not alter the chemical identity.

• Electrons, located in the outer shells, are crucial for forming ions.
• When atoms gain or lose electrons, they become ions with a net charge, differing from neutral atoms.

Understanding atomic structure aids in grasping how ions form and behave. Only changes in electron count impact ion formation, illustrating why options involving protons or neutrons are incorrect for ion formation.