Metals occupy the large majority of the periodic table, filling most of the left side and center. Out of 118 known elements, 93 are classified as metals. They stretch from Group 1 on the far left through Group 12 in the middle, and include several elements in Groups 13 through 16 on the right side. The dividing line between metals and nonmetals is a diagonal staircase shape that cuts across the right portion of the table.
The Staircase Line That Separates Metals From Nonmetals
If you look at a color-coded periodic table, you’ll notice a zig-zag line stepping down from the upper right toward the lower right. Everything to the left of that line is generally a metal. Everything to the right is a nonmetal. The elements sitting right along the line, like silicon, boron, arsenic, and antimony, are called metalloids because they share traits with both groups. They can look shiny like metals but shatter like glass.
Aluminum is worth noting because it sits right next to this staircase line, yet it behaves entirely like a metal. It conducts electricity, bends without breaking, and has a metallic shine. So despite its position near the boundary, it’s firmly in the metal category.
Alkali Metals: Group 1
The first column of the periodic table (Group 1) contains the alkali metals: lithium, sodium, potassium, rubidium, cesium, and francium. These are soft, highly reactive metals that tarnish quickly in air and react vigorously with water. They all form compounds with a simple one-to-one ratio with hydrogen, which reflects their shared chemistry.
Hydrogen also sits in Group 1 on most periodic tables, but it is not a metal. It’s placed there because it has a single electron in its outer shell, just like the alkali metals. But hydrogen’s ionization energy (the energy needed to strip that electron away) is 1,312 kJ/mol, more than double lithium’s 520 kJ/mol. That makes hydrogen far more reluctant to behave like a metal. Some periodic tables place hydrogen above the halogens instead, reflecting the fact that it can also gain an electron like a nonmetal.
Alkaline Earth Metals: Group 2
The second column (Group 2) holds the alkaline earth metals: beryllium, magnesium, calcium, strontium, barium, and radium. These are harder and less reactive than the alkali metals, but they still react with water and air. Magnesium and calcium are the most familiar, playing major roles in everyday life from fireworks to bone structure.
Transition Metals: Groups 3 Through 12
The wide block in the center of the periodic table, spanning Groups 3 through 12, contains the transition metals. This is where you’ll find iron, copper, gold, silver, platinum, nickel, zinc, and many other well-known metals. These elements are typically hard, dense, and excellent conductors of heat and electricity. Many of them can form compounds in multiple oxidation states, which is why transition metals produce such a wide range of colored compounds.
This block alone accounts for roughly 40 elements, making it the single largest category of metals on the table.
Post-Transition Metals: Groups 13 Through 16
Between the transition metals and the metalloid staircase line, you’ll find the post-transition metals. These include aluminum, gallium, indium, tin, thallium, lead, and bismuth. They sit in Groups 13 through 16, tucked in on the left side of the staircase. Post-transition metals tend to be softer and melt at lower temperatures than transition metals. They also have higher electronegativity, meaning they hold onto their electrons more tightly.
Tin and lead are probably the most recognizable members of this group. Both have been used by humans for thousands of years precisely because they’re easy to work with at relatively low temperatures.
Lanthanides and Actinides: The Bottom Two Rows
The two rows floating below the main body of the periodic table are the lanthanides and actinides, collectively called the inner transition metals. They technically belong between Groups 3 and 4 but are pulled out to keep the table from becoming impractically wide.
The lanthanides are 14 elements running from cerium (element 58) to lutetium (element 71). They’re all metals with reactivity similar to the alkaline earth metals in Group 2. Despite being called “rare earth elements,” several of them are actually fairly abundant in the Earth’s crust. They’re essential in magnets, rechargeable batteries, and smartphone screens.
The actinides span from thorium (element 90) to lawrencium (element 103). Uranium and plutonium are the most well-known members. All actinides are radioactive, and most of the heavier ones don’t exist in nature. They’ve been synthesized in laboratories, and nearly all of them behave as metals.
Why Metals Dominate the Table
Of the 90 naturally occurring elements, 66 are metals. When you add the 28 artificially produced elements (almost all of which are metallic or predicted to be), the count reaches 93 out of 118. That means roughly 80% of all known elements are metals.
This dominance comes down to atomic structure. Metals tend to have fewer electrons in their outer shells, which makes those electrons easy to share or lose. That free movement of electrons is what gives metals their defining characteristics: they reflect light (luster), conduct electricity and heat, can be hammered into thin sheets (malleability), and can be drawn into wires (ductility). As you move across a row of the periodic table from left to right, elements hold their outer electrons more tightly, which is why the nonmetals cluster on the right side.
A Quick Visual Guide
- Far left column (Group 1): Alkali metals (excluding hydrogen)
- Second column (Group 2): Alkaline earth metals
- Center block (Groups 3 through 12): Transition metals
- Right of center, left of the staircase (Groups 13 through 16): Post-transition metals
- Bottom two rows: Lanthanides and actinides (inner transition metals)
- Along the staircase line: Metalloids (not quite metals, not quite nonmetals)
- Right of the staircase (Groups 15 through 18): Nonmetals and noble gases
If you can picture the staircase line cutting diagonally from boron down to astatine, everything to its left (plus the two bottom rows) is metal territory.