Problem 5 - Biology: The Unity and Diversity of Life

Question

An ion is an atom that has ________. a. the same number of electrons and protons b. a different number of electrons and protons c. electrons, protons, and neutrons

Step-by-Step Solution

Answer

An ion is an atom with a different number of electrons and protons (option b).

Step 1: Understanding the Definition of an Ion

An ion is an atom or molecule that has gained or lost one or more electrons, giving it a net positive or negative electrical charge. This means that the number of electrons is not equal to the number of protons. Therefore, ions are formed by a difference between the number of electrons and protons in the atom.

Step 2: Analyzing the Options

Let's analyze the given options: - Option a states that an ion has the same number of electrons and protons, which we know is not true because this would result in a neutral charge, not an ion. - Option b states that an ion has a different number of electrons and protons, which matches our understanding of an ion's definition. - Option c talks about electrons, protons, and neutrons, but does not address the charge difference required for an ion.

Step 3: Selecting the Correct Option

Given our understanding that ions result from having a different number of electrons and protons, the correct choice is option b. This option correctly identifies that an ion is an atom with an unequal number of electrons and protons.

Key Concepts

Electrons and Protons

Electrons and protons are subatomic particles found within an atom. They play a crucial role in determining the chemical identity and electrical charge of the atom. Electrons are negatively charged particles, while protons are positively charged. The balance between the number of electrons and protons in an atom usually determines if the atom is electrically neutral or an ion.

• Electrons: Light, negatively charged particles that orbit the nucleus of the atom.
• Protons: Heavier, positively charged particles found in the nucleus.

When an atom has an equal number of electrons and protons, it is electrically neutral. However, if the number of electrons changes due to them being gained or lost, the atom becomes an ion, which holds an electrical charge.

Net Electrical Charge

The net electrical charge of an atom or molecule is determined by the difference between the number of protons and electrons. If there are more electrons than protons, the ion will have a net negative charge and is called an anion. Conversely, if there are more protons than electrons, the ion will have a net positive charge and is called a cation.

Calculating the net electrical charge is simple:

• If electrons = protons, Charge = 0 (neutral atom)
• If electrons > protons, Charge < 0 (anion)
• If electrons < protons, Charge > 0 (cation)

Understanding net electrical charge helps predict how atoms will interact in chemical reactions, as ions are often more reactive than neutral atoms.

Atom

An atom is the fundamental unit of matter and consists of a nucleus surrounded by electrons. The nucleus contains protons and usually neutrons, and is the dense central part of the atom. Atoms are incredibly small, yet they form the building blocks of everything we see around us.

Key components of an atom include:

• Nucleus: The core of the atom, containing protons and neutrons.
• Electrons: Clouds or shells of negative charge that surround the nucleus.

Atoms are usually neutral because they have the same number of electrons and protons. However, changes in the electron count can transform atoms into ions, dramatically affecting their chemical behavior and properties. Understanding atoms is essential to understanding the basic principles of chemistry and physics.