Themes

What is the metallic character?

The metallic character of the elements of the periodic table refers to all those variables, chemical and physical, that define metals or distinguish them from other substances in nature. They are generally shiny, dense, hard solids, with high thermal and electrical conductivities, moldable and ductile.

However, not all metals exhibit such characteristics; for example, in the case of mercury, this is a shiny black liquid. Likewise, these variables depend on the terrestrial pressure and temperature conditions. For example, seemingly non-metallic hydrogen can physically behave like a metal under extreme conditions.

These conditions can be: under abysmal pressures or very cold temperatures hovering around absolute zero. To define whether an element is metallic or not, it is necessary to consider patterns hidden from the observer’s eyes: atomic patterns.

These discriminate with greater precision and reliability which are the metallic elements, and even which element is more metallic than another.

Which of the coins is more metallic: a gold one, a copper one, or a platinum one? The answer is platinum, and the explanation lies in its atoms.

How does the metallic character of the elements vary in the periodic table?

The upper image shows the periodic properties of the elements. The rows correspond to the periods and the columns to the groups.

The metallic character decreases from left to right of the periodic table, and increases in the opposite direction. Also, the metallic character increases from top to bottom and decreases as the periods are traversed to the group heads.

In this way, the elements that are close to the direction to which the arrow points, have a greater metallic character than those located in the opposite direction (the yellow blocks).

Additionally, the other arrows correspond to other periodic properties, which define in what sense these increase or decrease as the element “metallizes”. For example, the elements of the yellow blocks, although they have low metallic character, their electronic affinity and ionization energy are high.

In the case of atomic radii, the larger they are, the more metallic the element is; this is indicated by the blue arrow.

Properties of metallic elements

The periodic table shows that metals have large atomic radii, low ionization energies, low electronic affinities, and low electronegativities. How to memorize all these properties?

The point at which they flow is the reactivity (electropositivity) that defines metals, which oxidize; that is, they lose electrons easily.

When they lose electrons, metals form cations (M + ). Therefore, elements with a higher metallic character form cations more easily than those with a lower metallic character.

An example of this is to consider the reactivity of group 2 elements, the alkaline earth metals. Beryllium is less metallic than magnesium, and magnesium is less metallic than calcium.

So on until reaching the metal barium, the most reactive of the group (after radium, a radioactive element).

How does the atomic radius affect the reactivity of metals?

As the atomic radius increases, the valence electrons are further from the nucleus, so they are held less strongly in the atom.

However, if a period is traversed to the right side of the periodic table, the nucleus adds protons to its now more positive body, which attracts valence electrons with greater force, reducing the size of the atomic radius. This results in a decrease in the metallic character.

Thus, a very small atom with a very positive nucleus tends to gain electrons instead of losing them (non-metallic elements), and those that can both gain and lose electrons are considered metalloids. Boron, silicon, germanium, and arsenic are some of these metalloids.

On the other hand, the atomic radius also increases if there is new energy availability for other orbitals, which occurs when descending in a group.

For this reason, when descending on the periodic table, the radii become bulky and the nucleus becomes unable to prevent other species from snatching electrons from its outer shell.

In the laboratory, with a strong oxidizing agent – such as dilute nitric acid (HNO 3 ) – the reactivities of metals against oxidation can be studied.

In the same way, the processes of formation of its metal halides (NaCl, for example) are also experiments demonstrating this reactivity.

Element of greater metallic character

Metallic character of the elements
Cesium

The direction of the blue arrow in the image of the periodic table leads to the elements francium and cesium. Francium is more metallic than cesium, but unlike the latter, francium is artificial and radioactive. For this reason, cesium takes the place of the natural element with the greatest metallic character.

In fact, one of the best known (and most explosive) reactions is the one that occurs when a piece (or drops) of cesium come into contact with water.

The high reactivity of cesium, also translated into the formation of much more stable compounds, is responsible for the sudden release of energy:

2Cs (s) + 2H 2 O → 2CsOH (aq) + H 2 (g)

The chemical equation allows us to see the oxidation of cesium and the reduction of hydrogens in water to hydrogen gas.

Element of minor metallic character

Metallic character of the elements
Fluorine 3D Model

On the opposite diagonal, in the upper right corner of the periodic table, fluorine (F 2 , top image) leads the list of non-metallic elements. Why? Because it is the most electronegative element in nature and the one with the lowest ionization energy.

In other words, it reacts with all the elements of the periodic table to form the ion F  and not F + .

Fluorine is very unlikely to lose electrons in any chemical reaction, quite the opposite of metals. It is for this reason that it is the least metallic element.

Related Articles

Leave a Reply

Your email address will not be published. Required fields are marked *

Back to top button