Periodic Table Explained- Elements and Properties

What Is the Periodic Table?

The periodic table is a chart that organizes all known chemical elements by their atomic number, electron configuration, and recurring chemical properties. It was designed to show patterns in behavior so chemists could predict how elements would react.

There are 118 confirmed elements currently on the table. Ninety-four occur naturally on Earth. The rest are synthetic, created in laboratories through nuclear reactions.

You probably saw this chart hanging in every science classroom you've ever entered. What you may not have realized is how much information it actually contains. Most people ignore 90% of what's there.

The History Behind It

Dmitri Mendeleev created the first recognizable version in 1869. He arranged elements by atomic mass and noticed properties repeated at regular intervals. When gaps appeared in his arrangement, he predicted elements would be discovered to fill them. He was right.

Other scientists attempted similar arrangements before him, but Mendeleev's version worked because he prioritized chemical behavior over strict numerical ordering. When the atomic number concept emerged years later, it confirmed his approach was correct.

The table has been expanded several times since then. The most recent additions were elements 113, 115, 117, and 118, officially recognized in 2016.

How the Table Is Organized

Rows: Periods

There are 7 horizontal rows called periods. Each period corresponds to the highest energy level of electrons in that row's elements.

As you move left to right across a period, elements gain protons and electrons. Their properties change predictably—metals give way to nonmetals.

Columns: Groups

There are 18 vertical columns called groups. Elements in the same group share similar chemical behavior because they have the same number of electrons in their outer shell.

This is the most useful feature of the table. If you know how one element in a group behaves, you can make educated guesses about others.

The Three Main Sections

• Metals — about 80% of the table. Generally shiny, malleable, good conductors of heat and electricity.
• Nonmetals — located in the upper right corner. Poor conductors, often gases at room temperature.
• Metalloids — the stair-step line between metals and nonmetals. They have properties of both.

The Blocks

The table is also divided into blocks based on electron orbital filling:

• s-block — left two columns plus helium
• p-block — right six columns
• d-block — the transition metals in the middle
• f-block — the lanthanides and actinides usually shown below the main table

Reading the Information on Each Element

Every element square contains specific data. Here's what you're looking at:

• Atomic number — the number of protons in the nucleus. This defines the element.
• Element symbol — one or two letters representing the element (H for hydrogen, He for helium).
• Atomic mass — the average weight of protons and neutrons. Listed at the bottom of each square.

The atomic number is always an integer. The atomic mass often isn't, because it accounts for isotopic variation in naturally occurring elements.

Key Element Groups and Their Properties

Alkali Metals (Group 1)

Lithium, sodium, potassium, rubidium, cesium, and francium. These are soft, highly reactive metals that don't occur freely in nature. Sodium and potassium are familiar because they form common salts. They explode when exposed to water.

Alkaline Earth Metals (Group 2)

Magnesium, calcium, and similar elements. Less reactive than alkali metals but still require caution. Calcium is essential for bones and teeth. Magnesium is critical for muscle function.

Halogens (Group 17)

Fluorine, chlorine, bromine, iodine, and astatine. These are the most reactive nonmetals. Chlorine disinfects water. Fluorine strengthens teeth. Iodine is essential for thyroid function.

Noble Gases (Group 18)

Helium, neon, argon, krypton, xenon, and radon. These elements don't react with anything under normal conditions. Their outer electron shells are full, so they have no reason to bond. This makes them useful for applications where chemical inertness matters.

Transition Metals

The 40 elements in the middle block. Copper, iron, gold, silver—these are transition metals. They tend to be hard, shiny, good conductors, and capable of forming multiple charged ions. Most of the metals you interact with daily fall into this category.

Element Categories Comparison

Common Uses for Periodic Table Knowledge

You don't need a chemistry degree to use this information practically.

• Predicting chemical reactions — Elements in the same group behave similarly. If sodium reacts violently with water, so will potassium.
• Understanding material properties — Why is copper used for wiring? It's in the right group with the right conductivity.
• Identifying hazards — Alkali metals and halogens are reactive and often dangerous. Knowing where they sit helps you understand risks.
• Reading ingredient labels — Element symbols appear in chemical names. NaCl is sodium chloride—table salt.

Getting Started: How to Use the Table

Here's a practical approach if you want to actually learn this:

1. Start with the first 20 elements. Memorize their symbols, atomic numbers, and approximate atomic masses. This covers the most common elements you'll encounter.
2. Learn the group names. You don't need to memorize every element, but knowing where alkali metals, halogens, and noble gases sit helps enormously.
3. Practice reading element squares. Pick an element you don't know. Identify its atomic number, mass, and position. Look up what it does.
4. Notice the patterns. Reactivity increases as you move down Group 1. Atomic mass increases as you move right and down. The table is designed to show these relationships.
5. Use it when problems arise. When you see a chemical equation or compound name, reference the table. Context makes retention easier.

What About Synthetic Elements?

Elements 95 through 118 were created artificially. Scientists smashed lighter atoms together and hoped the resulting nucleus would hold together long enough to measure.

Most synthetic elements exist for fractions of a second. Some have no practical applications yet. They were added to complete the table, not because anyone needed them.

The heaviest synthetic elements require increasingly extreme conditions to create. At some point, the nucleus becomes too large to maintain stability. This is why element 118 (oganesson) is probably close to the practical limit.

The Bottom Line

The periodic table works because elements show predictable patterns. Mendeleev noticed this in 1869, and it still holds true. If you understand the structure—periods, groups, blocks—you can navigate it effectively.

You don't need to memorize all 118 elements. You need to understand why they're arranged the way they are. That single concept makes everything else fall into place.