General Chemistry Explained in 19 Minutes

Chemistry can feel overwhelming with its complex equations, strange symbols, and intricate concepts. But at its core, it’s the study of how atoms—tiny building blocks of everything—interact. In this article, we’ll explore key topics from atomic structure to chemical reactions, offering a solid foundation in general chemistry.

Page Contents

What Are Atoms?

Everything around us—yes, even you—is made of atoms. These tiny units consist of a nucleus containing protons and neutrons, with electrons buzzing around it. The number of protons in an atom’s nucleus determines the element. For example:

Hydrogen (1 proton) is the simplest element.
Oxygen (8 protons) is essential for life.
Sodium (11 protons) is a shiny metal that reacts explosively with water.

Atoms combine to form molecules, like H₂O, which makes up water. They can also create compounds, such as NaCl (table salt), with properties entirely different from their individual elements.

The Periodic Table: Your Chemistry Roadmap

The periodic table organizes all known elements based on their atomic structure and properties. Here’s how to decode it:

Groups (Columns): Elements in the same group share the same number of valence electrons, which influence how they react. For instance, Group 1 (alkali metals) elements like sodium are highly reactive.
Periods (Rows): Elements in the same period have the same number of electron shells.

The periodic table also divides elements into three broad categories:

Metals (good conductors of heat and electricity),
Nonmetals (often gases or brittle solids), and
Semimetals (elements with properties of both).

Isotopes and Ions: Variations in Atoms

Not all atoms of an element are identical:

Isotopes have the same number of protons but different numbers of neutrons. Some are stable, while others decay and release radiation.
Ions are atoms that gain or lose electrons, giving them a charge. Positive ions (cations) lose electrons, while negative ions (anions) gain them.

For example, chlorine can exist as a neutral atom or as a chloride ion (Cl⁻) after gaining an electron.

Why Do Atoms Bond?

Atoms bond to achieve a stable electron configuration, typically a full outer shell. This drive for stability leads to three main types of bonds:

Covalent Bonds: Atoms share electrons to fill their shells.
Ionic Bonds: One atom donates electrons to another, creating oppositely charged ions that attract each other (e.g., NaCl).
Metallic Bonds: In metals, valence electrons move freely, allowing properties like electrical conductivity and malleability.

Intermolecular Forces: Molecules Interact

Even after atoms bond to form molecules, those molecules can attract each other through intermolecular forces:

Hydrogen Bonds: Strong attractions between molecules like water.
Van der Waals Forces: Weak, temporary attractions caused by electron movement.

These forces explain why water has a high boiling point and why oil and water don’t mix—oil is nonpolar, while water is polar.

States of Matter and Phase Changes

Matter can exist as solids, liquids, gases, or plasma, depending on temperature and pressure.

Solids: Particles are tightly packed in a fixed structure.
Liquids: Particles move freely but stay close together.
Gases: Particles move independently and fill their container.

As temperature increases, particles gain energy, causing solids to melt into liquids and liquids to evaporate into gases. These phase changes depend on energy (temperature) and the strength of intermolecular forces.

Chemical Reactions: Rearranging Matter

A chemical reaction occurs when bonds between atoms break and new ones form, creating different substances. Common types of reactions include:

Synthesis: Combining substances to form a compound (A + B → AB).
Decomposition: Breaking down a compound (AB → A + B).
Replacement: Atoms swap places (A + BC → AC + B).

Reactions release or absorb energy, depending on whether they are exothermic (releasing heat) or endothermic (absorbing heat).

Acids, Bases, and pH

Acid-base chemistry is central to understanding reactions in solutions.

Acids donate protons (H⁺ ions).
Bases accept protons.
The pH scale (0–14) measures the acidity or basicity of a solution. Pure water is neutral with a pH of 7, while lemon juice (acidic) has a lower pH, and soap (basic) has a higher pH.

When acids and bases mix, they neutralize each other, forming water and a salt.

Energy in Reactions: Will It Happen?

Whether a reaction occurs spontaneously depends on Gibbs Free Energy (ΔG), which factors in:

Enthalpy (ΔH): The heat content.
Entropy (ΔS): The disorder of a system.

A reaction with negative ΔG is spontaneous, while a positive ΔG requires added energy. Temperature can influence spontaneity, such as ice melting only when the temperature is above 0°C.

Quantum Chemistry and Electron Configurations

Electrons don’t orbit atoms like planets around the sun. Instead, they exist in specific energy levels, described by quantum numbers. These determine an atom’s electron configuration, which explains its chemical behavior. For example, sodium’s configuration is 1s² 2s² 2p⁶ 3s¹, showing one valence electron.

Wrapping It Up

This article covers the essential principles of general chemistry, from atomic structure to chemical reactions. Mastering these basics opens the door to more advanced topics like organic chemistry and thermodynamics. Whether you’re studying for exams or exploring for fun, chemistry reveals the fascinating ways matter interacts to create the world around us.