Question

$$ \text { What is an atom? } $$

Short answer

An atom is the smallest unit of an element, consisting of protons, neutrons, and electrons.

Step-by-step solution

Understanding the Atom

An atom is the fundamental building block of matter. It is the smallest unit of an element that retains the properties of that element.

Components of an Atom

Atoms consist of three primary types of particles: protons, neutrons, and electrons. Protons and neutrons make up the nucleus at the center of the atom, while electrons orbit around the nucleus.

Significance of Subatomic Particles

Protons carry a positive charge and define the atomic number, electrons have a negative charge and orbit the nucleus, and neutrons are neutral, contributing to the atom's mass.

Key concepts

Subatomic Particles

Subatomic particles are the tiny building blocks that make up an atom. There are three main types of subatomic particles:

• Protons: Positively charged particles located in the nucleus of an atom.
• Neutrons: Neutral particles with no charge, also found in the nucleus.
• Electrons: Negatively charged particles that move around the nucleus in orbits.

These particles are fundamental to the atom's structure and determine the properties of the element. Understanding subatomic particles is crucial for grasping how atoms form molecules and engage in chemical reactions.
Each type plays a unique role in the atom's identity and behavior. For example, the number of protons decides the element's identity, while the arrangement of electrons determines how atoms interact with each other.

Atomic Structure

The atomic structure refers to the arrangement of subatomic particles within an atom. The nucleus, a dense center, contains protons and neutrons. Around the nucleus are shells or energy levels where electrons orbit.

• The nucleus holds the vast majority of an atom's mass due to the heavy protons and neutrons.
• Electrons are much lighter and occupy vast spaces around the nucleus, creating an electron cloud.
• Energy levels or "shells" determine where electrons spend most of their time.

This structure is vital to understanding how atoms retain stability and react with other atoms. The specific energy levels can hold only a certain number of electrons, influencing chemical bonding and molecular formation.

Protons and Neutrons

Protons and neutrons are both located in the atom's nucleus, and they play crucial roles in the atom’s identity and stability.

• Protons: Each proton has a positive charge and a mass of approximately 1 atomic mass unit (amu). The number of protons in an atom defines the element and its place in the periodic table. This number is called the "atomic number." A greater number of protons than electrons results in a positively charged ion.
• Neutrons: Neutrons have no charge and a similar mass to protons. Their primary role is to stabilize the nucleus by offsetting the repulsive forces between protons. The number of neutrons can vary within the same element, leading to different isotopes, which can have distinct physical properties.

Together, protons and neutrons give an atom its mass and directly influence its nuclear stability.

Electrons

Electrons are negatively charged particles that orbit the nucleus of an atom. They are lightweight and move in specific patterns or "shells."

• Due to their negative charge, electrons are attracted to the positively charged protons in the nucleus.
• The movement of electrons in energy levels, also known as shells, allows for the formation of chemical bonds between atoms.
• The distribution of electrons across these shells follows the "octet rule," which states that atoms tend to be stable when they have eight electrons in their outer shell.

Electrons play a key role in chemical reactions, as they are the particles involved in forming or breaking bonds with other atoms. Their arrangement in an atom determines the atom's chemical properties and how it will react with other atoms.