Metals Non-Metals and Metalloids

Metals, Metalloids, and Non-Metals on the Periodic Table

As a starting point, let's review the periodic table's structure. In the periodic table, elements are arranged according to their atomic number. Symbols are unique to each element, and each element belongs to a specific group and period (figure 1). For example, the element magnesium (Mg) is located in period 3, Group 2.

Interestingly, the periodic table also separates the elements into metals, non-metals, and metalloids (figure 2). On the left side of the zig-zag line, you will find metals (except hydrogen, which is a non-metal).

• Elements in Group 1, except for hydrogen, are known as the Alkali Metals.
• Elements in Group 2 are known as the alkaline earth metals.
• Elements in groups 3 to 12 are called the Transition Metals.

The elements located on the right side of the zig-zag line are the non-metals. Elements in group 17 are called the halogens, while those in group 18 are known as the noble gases.

The elements located along the zig-zag line are the metalloids. These are boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium (Te), polonium (Po), astatine (At), and tennessine (Ts).

Properties of Metals

Now that we know which elements in the periodic table are metals, let's talk about its properties. As a general rule, metals have the following properties:

• They are shiny and possess metallic luster.

• Most metals are hard, with the exception of metals like potassium, sodium, and magnesium (they are easy to cut).

• Metals can be worked into thin sheets because they are malleable.

• Most metals are ductile and can be made into wires. For example, electric wires are usually made from copper and aluminum.

• Electricity and heat are conducted well by metals. This is why copper wires are commonly used in electrical appliances, and cooking utensils are typically made of iron, copper, and aluminum.

• At room temperature, all metals (except mercury) are solids.

Alkali Metals

The Alkali Metals (Group 1) are lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr). Metals in this group are very reactive and can cause explosions when placed in water or exposed to air.

• When any metal is burned in the presence of oxygen, it combines with oxygen to form a metal oxide.

• When any metal reacts with oxygen from the water (H₂O), they form a metal hydroxide.

Due to their reactivity, there are not found pure in nature. So, they need to be refined in a laboratory and contained in glass cases to avoid them from reacting with air.

Alkali metals are solids at room temperature, shiny, very soft and not dense. They are also good conductors of electricity and heat, and possess low melting points.

For example, potassium (K) is a soft, waxy metal that is highly reactive. When allowed to react with water, it forms potassium hydroxide and releases hydrogen gas.

Alkaline Earth Metals

The elements in group 2 are the alkaline earth metals. They are also reactive and shiny, so they are rarely found in their pure form in nature. They are firmer and denser compared to the alkali metals, and found as solids at room temperature. Group 2 metals tend to have high melting points ranging from 650 °C up to 1287 °C.

The elements found in group 2 are beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra).

Radium (Ra), for example, is the last element in this group. Radium is a radioactive metal, so its nuclei is capable of undergoing alpha (α) or beta (β) decay.

Transition Metals

Next, we have the transition metals. This is the largest category on the periodic table, consisting of elements in groups 3 to 12. Transition Metals (except for mercury), have a shiny metallic appearance, and high melting points.

Post-transition Metals

Some metals are considered post-transition metals, and these metals are found in groups 13 and 14. Like most metals, they are ductile and good conductors of heat and electricity. Post-transition metals are softer and have lower melting points compared to other metals.

Post-transition metals include aluminum (Al), gallium (Ga), indium (In), thallium (Th), tin (Sn), lead (Pb), and bismuth (Bi).

Lanthanoids and Actinoids

Lanthanoids (or lanthanides), are the elements with atomic numbers 57 to 71 in the periodic table. These elements are all metals that are commonly found in the Earth's crust as part of compounds with other elements. Their properties are similar to those of transition metals. They are also reactive and can tarnish easily in the presence of air.

Actinoids (or actinides) are all radioactive metals, mostly artificially produced in laboratories. Elements in this category have atomic numbers 89 through 103.

Properties of Non-Metals

Now, let's dive into the properties of non-metals. Non-metals are found in groups 14-18, and they are poor conductors of heat and electricity. Non-metals also lack metallic luster, are not malleable or ductile, and are found in different States of Matter at room temperature (mostly as gases). They also tend to have low melting points.

For example, sulfur (S) is a non-metal. It has a dull, yellow appearance and is brittle. Sulfur is also a poor conductor and heat or electricity, making it a good insulator. The melting point of sulfur is 113 °C.

Another property that is very important to determine whether an element is a metal or a non metal is Electronegativity. Non-metals tend to have higher Electronegativity compared to metals. Therefore, reaction between metals and non-metals yield ionic compounds.

The most electronegative element in the periodic table is fluorine (Figure 3). Notice that, when dealing with electronegativities, we do not count nobles gases (group 8) because they do not gain, lose or share electrons!

Figure 3. Periodic table trends in electronegativity, created with canva.

Halogens and Noble Gases

The non-metals in group 17 are called the halogens. These elements exist as diatomic molecules: F₂, Cl₂, Br₂, and I₂. Halogens are very chemically reactive and large electron affinities.

• Electron affinity is the energy change for gaining an electron.

In group 18, we have the noble gases. These elements have very little chemical reactivity (very unreactive) and exist as monatomic gases at room temperature. Noble gases also have high ionization energies.

• The energy needed to remove an electron is called ionization energy.

Chemistry of Non-Metals

Non-metals have many chemical properties. Chemical properties are properties of matter that are observed during a chemical reaction.

For starters, most non-metals (except for group 18) readily form compounds with other elements. Non-metals tend to gain electrons in reactions with metals to form negative ions.

For example, in the reaction between sodium (metal) and chlorine (non-metal), chlorine would take up an electron from sodium, becoming a negatively charged ion (Cl^-), while sodium would become positively charged due to losing an electron (Na⁺). Since sodium and chlorine ions are oppositely charged, they attract each other and are held together (NaCl) by strong electrostatic forces of attraction!

Non-metals can also share electrons with another non-metal in a covalent bond. For example, Carbon dioxide (CO₂) is a molecule composed of the non-metals Carbon and oxygen. These atoms are joined together by double covalent bonds (Figure 5).

$$ \text{SO}_2\text{ + H}_2\text{O }\longrightarrow \text{H}_{2}\text{SO}_{3} $$

Properties of Metalloids

Lastly, let's look at the properties of metalloids. As we learned before, metalloids are found along the imaginary zig-zag line. As, what is interesting about these elements is their characteristics are basically a mix of those seen on metals and non-metals.

Metalloids are solids at room temperature, hard, brittle and somewhat reactive. Metalloids vary in their ability to conductor electricity, and some are even used as semiconductors. Silicon (Si), for instance, is a metalloid that is greatly used in the manufacturing of microchips for computers.

Boron (B) is a metalloid that has many applications. For example, Boron carbide is a very hard substance that is used in the armor of military tanks!

Now, I hope that you feel more confident in your understanding on identifying metals, non-metals, and metalloids.