By Ron B. Davis Jr., Georgetown University
Their legendary toughness combined with their light weights have made many of the third- and fourth-row early transition metals popular alloying materials, whether to help increase the strength or decrease the weight of other metals. Let’s learn more about vanadium, titanium, and molybdenum.
Vanadium and Ford Model T
Just a tiny amount of vanadium can make a steel alloy much stronger. In 1908, Henry Ford chose vanadium steel as the material for high-stress components in his famous Model T, and is even said to have once declared, “But for vanadium there would be no automobiles!”
It is easy to see why he felt that way. A 2008 article in Popular Mechanics listed his choice of vanadium steel as second only to adoption of the assembly line in the success of Ford’s legendary Model T.
But as important as vanadium was for the Model T, Ford was only partially correct. There are other elements that can do vanadium’s job in steel formulations. Vanadium’s neighbors, chromium and molybdenum beneath it, have a similar effect, hardening steel and increasing steel’s corrosion resistance.
Interestingly, when it comes to vanadium, which has to lose five electrons to reach a noble gas configuration, the simple octet rule is no longer a reliable guide. Vanadium doesn’t need extreme conditions to oxidize in more than one way.
Although, it’s still possible for vanadium to take a +5 oxidation state, consistent with a loss of five electrons to reach a noble gas configuration. That’s how vanadium often combines with oxygen, forming the V2O5 oxide.
But vanadium can also quite easily take on the ++4, +3, and +2 oxidation states as well, losing only some of its outermost electrons.
Spectacularly, with each oxidation state of vanadium, comes new d-subshell electron transitions that can absorb differing colors. Changing the oxidation state of dissolved vanadium, or even just changing the pH of the solution in which it is dissolved, can produce what can only be called a rainbow of potential colors.
In 1801, Spanish-Mexican mineralogist, Andres Manuel del Rio, was the first to discover this element- number 23. Unfortunately, early attempts to validate his discovery erroneously concluded that del Rio’s sample only contained chromium, an element already discovered. Ultimately, del Rio’s discovery would be claimed and named by Swedish chemist, Nils Gabriel Sefström, some 30 years later.
This article comes directly from content in the video series Understanding the Periodic Table. Watch it now, on Wondrium.
Titanium is special—and not just for the fact that it is a remarkably lightweight element that can be used in alloys. Titanium is also special because it is the first example of a transition metal to exhibit more than one valence state. And yet, titanium begins to deviate from what the octet rule might predict.
For titanium, its outermost electrons are not screened as effectively from its nucleus as they would be in the larger atoms from the group, zirconium or hafnium. Hence, titanium’s electrons are held a little more tightly. That makes it a bit more difficult to remove all four electrons from a neutral titanium atom to create the titanium (IV) ion that would have a noble-gas configuration.
Now, for the most part, four electrons often can be removed to form titanium (IV), as is the case in titanium dioxide. Titanium dioxide is highly valued in paint and pigment industries because of its high opacity and white color when powdered.
This makes titanium dioxide something of a blank canvas that can form opaque-colored materials when pigments are mixed with it.
And yet, a little like how tin and lead sometimes settle for losing only their p-subshell electrons, titanium can, under much more unusual conditions, be forced into settling for loss of only its outermost 4s-subshell electrons, leaving it with a a +2 charge. But cases of titanium settling for loss of fewer electrons is usually observed only under very extreme conditions, like the surface of stars or the atmospheres of exoplanets.
When it comes to colorful chemistry, it is not only the third-row d-block metals that have a monopoly! Just below chromium, for example, is another colorful element molybdenum.
Molybdenum is one of the hardest metals, with one of the highest-known melting points. The strange fact that it was named using a Greek word for ‘lead’ was because one of its common compounds, molybdenum sulfide—was known to have soft properties resembling actual lead.
In its pure, metallic state, molybdenum is a silvery-white metal. But just like chromium above it on the table, molybdenum can adopt many different oxidation states in which its 4d electron subshell is partially filled. In fact, known oxidation states of molybdenum range from -1 to +6!
One might have heard of ‘chromium-steel’ by its more common name, stainless steel. ‘Chromium-molybdenum steel’ is sometimes referred to as ‘chrome moly steel’. Both of these lighter, tougher metals owe many of their improved properties to the inclusion of these early transition metals into the structure of iron.
Even chromium’s neighbor to the right, manganese gets in on the action. It was used to produce one of the first steel alloys ever, combining it with iron to produce a product ‘mangalloy.’
Scientists have developed ways to use molybdenum’s remarkable chemistry and color to develop a sensitive test for the presence of other elements. The material commonly known as molybdenum blue, for example, is a complex substance containing both molybdenum (V) and molybdenum (VI) ions.
Making Beautiful Colored Compounds
When molybdenum blue is exposed to reducing materials—materials that give it some electrons—some of the molybdenum (VI) ions take on an extra electron, converting them into molybdenum (V). As the population of each oxidation state changes, so does its contribution to the color of the sample.
By carefully measuring this color change, chemists can use molybdenum to determine the concentration of other elements like phosphorous, arsenic, and silicon.
Although many transition metals are indeed capable of making beautiful colored compounds when combined with other elements, molybdenum and its neighbors on the table are probably best known for their uses as pure metals or alloys in engineering and construction.
Common Questions about Vanadium, Titanium, and Molybdenum
Vanadium’s discovery was claimed by Swedish chemist Nils Gabriel Sefström.
Titanium dioxide is highly valued in paint and pigment industries because of its high opacity and white color when powdered.
Molybdenum is one of the hardest metals, with one of the highest-known melting points.