Metals And Non-Metals

This posting will later be moved to the physics and astronomy blog, www.markmeekphysics.blogspot.com .

Remember, once again, the difference between the cosmology blog and the physics and astronomy blog. If a topic involves either outer dimensions of space that we cannot access, or space being composed of the infinitesimal negative and positive electric charges of my cosmological theory, then the topic is classified as cosmology. If this is not necessary to understand the given topic, it is classified as ordinary physics or astronomy.

The division of the chemical elements into metals and non-metals are so primary to life. But why are some elements metals, and others are non-metals? I have never seen a real explanation of this.

Here is a periodic table of the elements showing how many elements are metals, compared to non-metals: http://chemistry.about.com/od/periodictables/ss/Metals-Nonmetals-and-Metalloids-Periodic-Table.htm .

Here is a good interactive periodic table with a lot of information: www.ptable.com .

A metal is a chemical element in which large groups of atoms share their outer shell of electrons so that the outer electrons are, in effect, in an orbital around the entire group of atoms. The group of atoms sharing the outermost shell of electrons is referred to as a crystal, and the shared electrons are called delocalized electrons. It is these shared outer electrons that give metals their metallic luster, and make it possible for the metal to conduct electricity when a voltage pressure is applied to move these outer electrons.

A non-metal element, in contrast, has it’s electrons in orbitals only around it’s own nucleus, unless the non-metal atom is in a covalent bond with another atom. In a covalent bond, in contrast to an ionic bond based on two adjacent atoms with net opposite charges, atoms combine to form a molecule by sharing an outer electrons which “ties” them together.

In the posting “Atoms And Color”, on the physics and astronomy blog, we saw how the electron orbitals determine the color of matter and particularly metals.

The first clue as to why some elements are metals, and others are non-metals, is to be seen on the periodic table of the elements. The vast majority of elements are metals. The non-metals, with the exception of hydrogen, are confined to the upper right of the periodic table. There is a boundary region between the two, known as metalloids, which have characteristics of both metals and non-metals.

Just a review of basic chemistry. The periodic table is arranged somewhat like a calendar. The maximum number of electrons that any atom can have in it’s outer shell is eight. The first column, with hydrogen at the top, has one electron in the outermost shell. The last column, starting with nitrogen, has eight electrons in the outer shell of these atoms. This is why the elements of the rightmost column of the periodic table are chemically non-reactive, their outer electron shell, which governs all chemical behavior with the exception of the transition metals, is already full with eight electrons and this acts to preclude chemical activity. 

It is the electrons in the outermost orbital shell that determines the chemical behavior of the atom. Elements with one or two electrons in the outermost shell tend to lose those electrons in chemical reactions. Elements with six or seven electrons in the outermost shell tend to gain one or two more in chemical reactions. Elements with from three to five electrons in the outermost shell tend to share those electrons with other atoms to form molecular bonds.

There are two fundamental types of chemical bond between atoms, ionic and covalent. Atoms that gain or lose an outer electron in a reaction, thus gaining or losing a net electron and becoming an ion, form ionic bonds between the atom that lost the electron and the one that gained it because one now has a net positive charge and the other a net negative charge. Atoms that share electrons with other atoms form covalent bonds. Ionic bonds tend to be more brittle than covalent bonds. The chemistry of living things is based on the covalent bonds of carbon.

Most of the matter that we see around us appears to be non-metallic. But the majority of molecular compounds contain some metal atoms. A salt, for example, is the product of an acid-base reaction, consisting of a molecule of a metal and a non-metal. Ordinary table salt is a compound of sodium, a metal, and chlorine, a non-metal. This gives ordinary salt it’s chemical name of sodium chloride.

But what exactly is it that determines whether an element will be a metal or a non-metal? I have never really seen this explained.

The first thing that becomes clear by just a glance at the periodic table is that the closer to being full is the outermost shell of electron orbitals, and the greater the number of electrons in the outer shell relative to the total number of electrons in the atom, the more likely the element will be a non-metal. In reactions, metals tend to lose outer electrons while non-metals tend to gain them. The heavier an element is, the more likely it is to be a metal.

We could say that the higher the proportion of an element’s electrons are in the outer shell, the more likely is the element to be a non-metal. This makes sense because we can see by their relative positions on the periodic table that metals tend to lose electrons in reactions, while non-metals gain them.

My conclusion is that the separation of elements into the categories of metals and non-metals begins when the atoms are formed by the tremendous heat and pressure in the centers of stars. The gravity of the mass of the star reaches the point where it can overcome the electron repulsion between adjacent atoms and crunch smaller atoms together into larger ones. It is during this process that the atoms of each chemical element take the form of either a metal or a non-metal.

Imagine a large number of identical spheres together, representing the atoms in the center of a star. Each sphere will have six adjacent spheres, two each on opposite sides in each of the three spatial dimensions. There is electron repulsion between adjacent atoms, the force which prevents atoms from merging into one another because the outer electrons of both are negatively-charged and like charges repel.

As extreme pressure is applied to the spheres, adjacent spheres distort the shape of each other so that the spheres begin to resemble cubes rather than spheres. When the point is reached where adjacent atoms are shaped more like cubes than spheres, the electron repulsion can no longer hold the atoms apart and they crunch together into one. The former energy that was in the electron repulsion between the atoms is overcome and redirected into the binding energy that hold the new and larger nucleus together against the like-charge repulsive force of the positively-charged protons in the nucleus.

But when the sides of adjacent atoms that are in contact begin to resemble the sides of cubes, rather than spheres, that means that the electron orbitals in adjacent atoms are closer to be straight lines and parallel to one another. This adjusts the orbital direction of each of these parallel electrons to go off on a tangent, rather than to orbit the new nucleus that is being formed. Many other atoms nearby also have electrons that were in the outer orbital shells of the smaller atoms, before being crunched together, with their orbital paths also distorted and diverted to go off on a tangent rather than to continue in the spherical orbit around a nucleus. 

There are so many other new nuclei nearby, formed from the crunching process, that electrons off on a tangential course can be nearer to these than to the atoms from which they originated. Their original atoms do not miss their electric charges, the absence of which would bring about a charge imbalance, because other tangential electrons move in to take their places.

What ends up happening is that a large number of atoms have their outermost electrons displaced by the process of small atoms being crunched together into larger ones. These electrons are not lost, the strong bias against charge imbalance keeps them from going far. The atoms in the group fall into a pattern of sharing their outermost electrons. These groupings of atoms within metals that share their outermost electrons are referred to as crystals. There is energy in the higher multi-atom orbitals of these shared outer electrons which is a transformation of the kinetic energy of the mass of the star, which we saw in the posting "Metallic Energy" on this blog.

This is exactly what a metal is, an element consisting of groupings of atoms that share their outermost electrons, and this is the only plausible explanation that I can see of how metals come about. This scenario describes what happens during nucleo-synthesis in stars, because metals as elements are the rule rather than the exception. The delocalized electrons are what gives the metal it’s characteristic luster, and makes the conduction of electricity possible.

The next question concerns why, since the process of metal formation is so logical, all of the chemical elements in the periodic table are not metals. The answer lies in the outermost electron shell of each atom. Remember that metals, in chemical reactions, tend to lose their outermost electrons anyway.

The atoms of each element have an established electron configuration, the arrangement of the numbers of electrons in each orbital shell, that must be adhered to due to the attraction of opposite electric charges. But in elements that have few outermost electrons that it tends to lose in reactions anyway, or that have a lower proportion of their total electrons in the outermost orbital shell, there is the possibility of easily sharing these electrons among many atoms of the element and this is what brings about metals.

In the non-metals, the outermost shell of electron orbitals is more “important” to the individual atom than it is in metals. This is because non-metals have either more electrons or a higher proportion of their total number of electrons in the outermost orbital than metals. The powerful attraction of opposite charges that holds the atom together, the negative charges of the electrons and the positive charges of the protons in the nucleus, makes it far more difficult for these outer electrons to be shared among many atoms and no metallic structure of “community” electrons forms, because this would upset the charge balance of the atoms more than it would when metal atoms are forming.

Finally, I had wondered if there was some formula as to whether an element would be a metal or a non-metal, but have never seen such a formula. While working on this posting, and looking at the periodic table, I noticed a simple formula that would predict metallic characteristics of any chemical element.

The periodic table is structured much like a calendar. Just as each column on a calendar represents the same day of the week, each columnar group on the periodic table represents the same number of electron in the outermost electron orbital shell. Helium is an exception, it is grouped on the rightmost column because it's outer orbital is full. The atoms in a column tend to have similar chemical behavior because this chemical behavior is determined by the number of electrons in the outermost shell, how full or empty it is. Remember that the most electrons that can be in the outermost shell is eight, although that is not true of inner orbital shells.

The horizontal rows across the periodic table are similar in concept to the weeks on a calendar, starting with only one electron in the outer shell on the left of the table, and going to a full eight electrons in the outer shell on the right of the table. The columns and rows are both numbered, columns starting with 1 left and rows starting with 1 at the top. The lightest elements are to the top and to the left, the heaviest elements are to the right and the bottom.

I notice that if we simply compare the number of electrons in the outermost shell with the number of the row, it gives us an indication of how metallic the element is. If the number of electrons in the outermost orbital shell is greater then the number of the row, the element will be tend to be a non-metal meaning that there will not be large groups of atoms that share their outermost electrons. If the number of electrons in the outermost shell is not greater than the number of the row, the element will be more metallic. The metalloid elements, the boundary region between metals and non-metals, will have numbers of outer electrons that are about the same as the row number.

We could call this simple formula the Metallic Index.