Problem 4 - Campbell Biology

Question

Which statement is true of all atoms that are anions? (A) The atom has more electrons than protons. (B) The atom has more protons than electrons. (C) The atom has fewer protons than does a neutral atom of the same element. (D) The atom has more neutrons than protons.

Step-by-Step Solution

Answer

Option (A) is true: anions have more electrons than protons.

Step 1: Understand Anions

Anions are atoms or molecules that have gained one or more electrons, thus acquiring a net negative charge.

Step 2: Compare Electrons and Protons

Since anions have gained electrons, they must have more electrons than protons, since electrons are negatively charged and protons are positively charged.

Step 3: Eliminate Incorrect Options

Option (B) suggests that atoms have more protons than electrons, which contradicts the definition of anions. Option (C) says anions have fewer protons than neutral atoms, which is misleading because it implies a different number of protons. Option (D) talks about neutrons in relation to protons, which is irrelevant to defining anions.

Step 4: Confirm the Correct Option

Since more electrons than protons is consistent with the definition of an anion, option (A) is the correct choice.

Key Concepts

Atoms and Molecules

Atoms are the basic units of matter. Each atom consists of a nucleus, which contains positively charged protons and neutral neutrons, surrounded by negatively charged electrons.
These electrons orbit the nucleus in various energy levels or shells. Molecules, on the other hand, are formed when two or more atoms bond together chemically.
This bonding can occur through the sharing or transfer of electrons to achieve stable electron configurations.

Electron Gain

When an atom gains one or more electrons, it becomes negatively charged because electrons carry a negative charge.
This process of gaining electrons is fundamental in forming anions, which are negatively charged ions.
Atoms gain electrons to achieve a more stable electron configuration, often completing their outermost electron shell.

Negative Charge

The negative charge in anions results from the excess number of electrons compared to protons.
Electrons, being negatively charged, increase this negative charge when added to an atom.
The overall charge of an atom becomes negative (anion) when the number of electrons exceeds the number of protons within the atom.

Comparison of Electrons and Protons

Electrons and protons are subatomic particles with opposite charges.
Electrons have a negative charge, while protons have a positive charge, and they are both present in every atom.
The balance between these particles dictates an atom's net charge:

• If an atom has equal numbers of protons and electrons, it is neutral.
• If it has more electrons than protons, it becomes a negatively charged ion (anion).
• If it has fewer electrons than protons, it becomes a positively charged ion (cation).