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Transition Metals

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Chemistry

What does the word 'transition' mean to you? It comes from the Latin transientum, meaning 'passing over', and implies a passage from one place to another.

Well, that's what transition metals are - a group of elements that bridge the gap between two sides of the periodic table.

According to IUPAC naming conventions, transition metals are elements whose atoms have a partially filled d-subshell, or which form at least one stable ion with a partially filled d-subshell of electrons.

  • This article is an introduction to transition metals in inorganic chemistry.
  • We'll start by defining transition metals.
  • We'll then be looking at their location on the periodic table.
  • We'll look at their general properties.
  • Finally, we'll explore some of their uses and applications.

What are transition metals?

Scientists sometimes disagree on their exact classification. In fact, there are a few different definitions.

For your exams, you need to know the IUPAC definition we mentioned above. This includes most of the elements in the d-block of the periodic table. You can see this on the periodic table below. Here, the transition metals are highlighted in blue.

Transition Metals periodic table of elements with transition metals highlighted in blue StudySmarterPeriodic table of elements with transition metals highlighted. Olive Odagbu, StudySmarter Original

Sometimes the term transition metals is used to refer to all of the elements in the d-block. However, this isn't strictly correct since they don't all form stable ions with incomplete d-subshells of electrons. We'll take a look at why this is so later.

You might also see the lanthanides, which are elements with atomic number 57 - 71, and the actinides, which bear the numbers 89 - 103, referred to as inner transition metals. But for the purpose of this article, we'll stick to the IUPAC definition - just the elements highlighted in blue above.

Transition metals in the periodic table

As we showed you above, the transition metals are found in the middle of the d-block in the periodic table.

The d-block is a section of the periodic table. The highest energy subshell found in d-block elements is always a d-subshell. The d-block is found between the s- and the p-blocks, and provides a link between the two.

More specifically, transition metals are found in groups 3-12 and periods 4-7, but this isn't important - all that matters is that you can find them in the periodic table.

Electron configuration of transition metals

We'll start with their electron configuration as atoms, and then look at how this changes as they form ions. This will also help explain why certain members of the d-block aren't classified as transition metals.

This section probably won't make much sense if you haven't read Electron Shells and Electron Configuration. We'd recommend checking them out first to learn the basics of electron shells, sub-shells, orbitals, and filling rules.

Electron configuration of transition metal atoms

As we mentioned above, all transition metals are found in the d-block of the periodic table. This means that their valence electrons are all found in a d-subshell.

You should remember that electrons are found in shells. These are broken down into subshells. There are four different types of electron subshell: s-, p-, d- and f-subshells. An element's position in the periodic table tells you the highest energy subshell that their electrons are found in. The highest energy subshell found in p-block elements, for example, is a p-subshell.

As you move across the period in the periodic table, each transition metal has one more electron than the one before. These electrons gradually fill up the d-subshell, but there are a few sneaky exceptions. Let's take a closer look, using the first row of transition metals (period 4) as an example. We've highlighted the period below.

Transition Metals periodic table of elements with Period 4 highlighted in blue StudySmarterPeriodic table with Period 4 highlighted. Olive Odagbu, StudySmarter Original

Let's take a look at their electron configurations. As in the periodic table, we've highlighted the transition metals.

Transition Metals period 4 electron configuration StudySmarterThe electron configuration of period 4. Anna Brewer, StudySmarter Original

The first two elements in period 4, potassium (K) and calcium (Ca) are found in the s-block. Their valence electrons are found in the 4s-subshell, and their 3d-subshells are empty.

Remember that subshells fill up in a certain order, from lowest energy to highest energy. This usually follows the pattern of lowest number to highest number. For example, 2s fills up before 3s. However, 3d is an anomaly - it has a slightly higher energy than 4s and so fills up after 4s. This is just another example of an annoying exception to the rules that you need to learn!

The next 10 elements are d-block elements. As you go across the period, electrons are added to the inner 3d-subshell, one by one. For example, scandium (Sc) has 21 electrons and has just one electron in its 3d-subshell, giving it the electron configuration of [Ar] 3d1 4s2, whereas titanium has 22 electrons and has two electrons in its 3d-subshell. This gives it the electron configuration of [Ar] 3d2 4s2.

But as we mentioned above, this filling pattern is rudely interrupted by two elements: chromium (Cr) and copper (Cu). Both have partially filled 4s-subshells. Why is this the case?

Well, it is because the 4s- and 3d-subshells have very similar energy levels. Since the electron in the 4s-subshell is unpaired, it doesn't experience any electron-electron repulsion. This lowers its energy state and more than makes up for the extra electron in the slightly higher energy 3d-subshell. Electrons simply like being in the lowest energy state possible. It is also believed that having a half-full 3d-subshell, as in the case of chromium, or a completely filled 3d-subshell, in the case of copper, helps stabilise the atom.

Transition Metals difference between expected and observed subshells in Cr and Cu StudySmarterExpected and observed electron configurations of chromium and copper. Anna Brewer, StudySmarter Original

Electron configuration of transition metal ions

All transition metals form positive cations by losing electrons.

You might remember from Electron Configuration that although the 3d-subshell is of a slightly higher energy level than the 4s-subshell, atoms lose electrons from the 4s-subshell first. This means that all transition metals lost their 4s electrons before their 3d electrons.

Take iron (Fe) as an example. It commonly forms ions with charges of 2+ or 3+. Iron has the electron configuration of [Ar] 3d6 4s2. When forming a 2+ ion, it first loses its 4s electrons, giving it the electron configuration of [Ar] 3d6 4s0. To form a 3+ ion, it needs to lose a further electron. Since the 4s-subshell is now empty, this electron is lost from the 3d-subshell, giving the ion the electron configuration of [Ar] 3d5 4s0.

Transition Metals iron electron configuration StudySmarterThe electron configuration of iron, iron(II) and iron(III). Anna Brewer, StudySmarter Original

Why aren't all of the d-block elements transition metals?

This is because they don't all form stable ions with incomplete d-subshells. For example, scandium (Sc) only forms 3+ ions in all of its compounds, which gives it the electron configuration of [Ar] 3d0 4s0. Its 3d-subshell is completely empty, so it isn't a transition metal. Likewise, zinc (Zn) only forms 2+ ions in all of its compounds. These ions have the electron configuration of [Ar] 3d10 4s0. Its 3d-subshell is completely full, so it isn't a transition metal.

Properties of transition metals

Transition metals all have similar properties. They are good conductors of heat and electricity, are hard and strong, and have high melting and boiling points. Compared to group 1 and 2 metals, they are also relatively unreactive. This makes them extremely useful, but we'll explore that in the next section. For now, let's look at some of their other characteristic properties. There are four in particular that you need to know about when it comes to transition metals:

  1. Transition metals form ions with multiple oxidation states. We already looked at how iron forms both 2+ and 3+ ions.
  2. They form complex ions. Complex ions are ions bonded to other ions or molecules, known as ligands, using dative covalent bonds.
  3. They form coloured compounds. For example, copper often forms blue solutions.
  4. They are good catalysts, which are substances that increase the rate of a chemical reaction without being used up in the process.

We explore these properties in much more depth in Properties of Transition Metals.

Uses of transition metals

Because of their properties, transition metals have a wide variety of uses. You find them in electronics, building materials, and more. Here are some of their more common applications:

  • Aluminium is lightweight and non-toxic, so is used not only in the manufacture of car and aircraft parts, but also to make cans and foil for wrapping food.

  • Iron is used in building materials, for example in bridges, ships, and in the structural framework of buildings. This is due to its high strength and low cost. In fact, iron accounts for 90 percent of the world's metal production.

  • Copper is used in electrical wires because of its good electrical conductivity.

  • You might find powdered titanium in the pyrotechnics industry, such as in fireworks, because it produces brightly-burning particles.

  • Tungsten is used in light bulb filaments and X-ray tubes.

Transition metals often form alloys. These are compounds made from mixtures of elements, of which at least one is a metal. Alloys are generally stronger than pure metals. Metals form lattices, and in pure metals, the metal ions within the lattice are all the same size, so it is easy for them to slip over each other.

However, alloys contain different-sized metal ions. These distort the lattice and make it harder for the ions to slide over each other. Useful transition metal alloys include brass (made from copper and zinc), steel (made from iron and carbon, a non-metal), and sterling silver (made from silver and another metal, usually copper).

For more information about metal lattices, check out Metallic Bonding.

Transition Metals - Key takeaways

  • Transition metals are elements whose atoms have a partially filled d-subshell, or which form at least one stable ion with a partially filled d-subshell of electrons.

  • Transition metals are found in the d-block of the periodic table. This means that their highest energy subshell is always a d-subshell. More specifically, transition metals are found in groups 3-12 and periods 4-7.

  • Transition metals differ by the number of electrons in their d-subshells. However, copper and chromium have slightly different electron configurations than expected due to the similarity in energy levels of the 4s- and 3d-subshells.

  • When forming ions, transition metals lose their 4s electrons before their 3d electrons.

  • Transition metals are hard and strong, have high melting and boiling points, and are relatively unreactive.

  • Transition metals also form ions with multiple oxidation states, form complex ions, produce coloured compounds, and act as catalysts.

  • Transition metals are used as building materials and in electronics. They also form many different alloys.

Transition Metals

Transition metals are good catalysts as they can change their oxidation state, and they have the ability to adsorb other substances.

Transition metals are less reactive than other groups due to high ionization energy and high melting point.

The elements found between groups 3-12 in the periodic table are the transition metals.

They do not have a partially filled d-subshell in their atomic state or their common oxidation state (i.e., Zn2+, Sc3+), hence they are not regarded as transition elements.

Transition metals are metals whose atoms have a partially filled d-subshell, or which form at least one stable ion with a partially filled d-subshell of electrons. They are found between groups 3-12 on the periodic table.

Final Transition Metals Quiz

Question

Give a reason why you should use a container of the same dimensions for each sample when carrying out analyses using a colorimeter.


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Answer

You should use a container of the same dimensions because absorption is proportional to the distance travelled through the solution.


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Question

Why do we use a coloured filter in colorimetry?

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Answer

We use a coloured filter that matches the wavelength that the solution absorbs the most, this way maximum absorption can take place.


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Question

Write down the equation that shows the relationship between Planck’s constant, the energy change ∆E and the frequency of visible light. 


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Answer

∆E = hv = hc/𝝀


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Question

Explain whether a transition ion complex that forms a red solution absorbs a small or a large frequency.


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Answer

A red solution absorbs a large frequency of light from the blue end of the spectrum, since blue is the complementary colour of red.


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Question

State three features of transition metals that can alter ∆E

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Answer

  1. Oxidation state
  2. Ligands
  3. Coordination number


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Question

How does electron arrangement help classify a transition element?

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Answer

Transition elements form stable ions with a partially filled 3d subshell.

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Question

John thinks an unknown solution contains [Fe(H2O)6]2+ ions. To confirm it he reacts the solution first with aqueous ammonia, and then with aqueous sodium carbonate.

Write the equations for both reactions.

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Answer

Reaction with ammonia

Fe(H2O6)2+ + 2NH3 ➔ Fe(H2O)4(OH)2 + 2NH4+


Reaction with sodium carbonate

[Fe(H2O)6]2+ + CO32- ⟶ Fe(CO3) + 6H2O

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Question

What property of transition metals make them good catalysts?

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Answer

Their variable oxidation states.

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Question

In the reaction between ammonium vanadate and zinc in an acidic solution, what can you observe that shows vanadium has at least three oxidation states?

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Answer

The solution changes to three different colours.

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Question

Describe the colour changes you would observe if zinc is added to a solution of ammonium vanadate in hydrochloric acid.

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Answer

Colour changes from yellow to blue to green to violet.

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Question

How do you prepare Tollens' reagent and what do you observe?

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Answer

  1. Add some sodium hydroxide to silver nitrate to produce silver(I) oxide, a brown precipitate.
  2. Add ammonia solution to redissolve the silver(I) oxide back to diamminesilver(I). The solution is colourless.


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Question

How do you carry out the 'silver mirror' test and what happens if an aldehyde is present?

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Answer

  1. Add a few drops of the unknown organic compound to Tollens' reagent. 

  2. Then gently warm in a water bath.

  3. If it's a ketone, you will observe no change in the colourless solution

  4. If it's an aldehyde you will get a grey silver precipitate. The Ag+ ions have reduced to Ag and the aldehyde is oxidised to carboxylic acid.

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Question

Explain how the pH and ligand affect the redox potential of a transition ion going from a high oxidation state to a lower one.

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Answer

Transition ions are less willing to accept electrons in a neutral solution. 

Some ligands that are more firmly attached to the central ion make it difficult for a transition ion to lose electrons. 

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Question

Use the half equations below to give an ionic equation for the reaction between vanadate(V) and zinc.


VO2+ (aq) + 2H+ (aq) + e- ⇌ VO2+ (aq) + H2O (l)              Eº = +1.00 V


Zn (s) ⇌ Zn2+ (aq) + 2e-                                                                  Eº = -0.76 V

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Answer

2VO2+ (aq) + 4H+ (aq) + Zn (s)  ⟶ 2VO2+ (aq) + 2H2O (l) + Zn2+ (aq)

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Question

Why are transition metals good catalysts?


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Answer

Transition metals act as good catalysts as they can change their oxidation state, and have the ability to adsorb other substances.


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Question

Are transition metals reactive?

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Answer

Transition metals are less reactive than other groups due to high ionization energy and high melting point.


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Question

Which metals are transition metals?

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Answer

The elements between groups 3-12 in the periodic table are the transition metals.


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Question

Explain why Sc and Zn are not classified as transition metals. 


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Answer

They do not have a partially filled d-subshell in their atomic state or their common oxidation states (i.e., Zn2+, Sc3+), hence they are not regarded as transition elements.


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Question

What are some common uses of Ni and Ti?

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Answer

Nickel is mainly used in stainless steel, while titanium is used in fighter aircraft, among other things.



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Question

What are transition metals? 

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Answer

Transition metals are metals whose atoms have a partially filled d-subshell, or which form at least one stable ion with a partially filled d-subshell of electrons. 


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Question

Where do the transition metals lie in the periodic table?



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Answer

Transition metals are found between groups 3-12 in the periodic table.



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Question

What is interesting about the electron configuration of transition metals?



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Answer

An interesting observation is the fact that the 4s orbitals fill before the 3d orbitals since the latter have a slightly higher energy level.



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Question

In which order do transition metals lose electrons from the s- and d-subshells in order to form transition metal ions?



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Answer

They first lose electrons from the s-subshell and then lose from the d-subshell.




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Question

What are some characteristic properties of transition metals?



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Answer

  1. They form ions with multiple oxidation states. 

  2. They form complex ions. 

  3. They form coloured compounds. 

  4. They are good catalysts. 

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Question

Give a common use of copper.



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Answer

Copper is used to make water pipes.



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Question

Name a d-block metal which occurs as a liquid.

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Answer

Mercury (Hg)


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Question

Which property is typical of transition metals?



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Answer

They form different coloured ions.

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Question

Which of these elements is a transition element?



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Answer

Cu

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Question

What are some characteristic physical properties of transition metals?



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Answer

They are metallic, good conductors of heat and electricity, hard, shiny, high MP, high BP.



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Question

Between Ti2+ and V2+, which ion contains more unpaired electrons?



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Answer

V2+

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Question

Between V2+ and Fe2+, which ion contains more unpaired electrons?


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Answer

Fe2+

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Question

Why do transition metals show magnetic properties?



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Answer

Since most of the transition ions or their compounds have unpaired electrons in the d-subshell, this means that they are paramagnetic. In other words, they show magnetic properties.

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Question

What are five physical properties of transition metals?

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Answer

1. High melting and boiling points

2. Metallic character

3. Strong

4. High thermal conductivity

5. High electrical conductivity



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Question

What are the characteristic properties of transition elements?

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Answer

1. Complex ion formation

2. Formation of coloured compounds

3. Variable oxidation states

4. Catalytic activity



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Question

Why do transition metals have different properties from main-group elements?



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Answer

Transition metals have different properties due to the fact that they can lose electrons from the inner d-subshell, apart from the outer s-subshell. 



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Question

Why do transition metals have variable oxidation states?



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Answer

The variable oxidation states of transition metals is due to the very similar energy levels of the s and d-orbitals, enabling electrons to be lost from both types of orbitals. 



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Question

What is the difference between paramagnetic and diamagnetic substances?



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Answer

Paramagnetic substances are attracted to a magnetic field due to the presence of unpaired electrons, whilst diamagnetic particles are repelled by a magnetic field, due to the fact that all electrons are paired.



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Question

What are complex compounds?



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Answer

Complex compounds are ones in which a central transition metal ion is bonded to a number of ions or neutral molecules by co-ordinate bonds. Such ions or neutral molecules are called ligands. 



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Question

Give an example of the catalytic use of a transition metal.



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Answer

Nickel is used as a catalyst in hydrogenation reactions.



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Question

Why do transition metals form coloured compounds?



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Answer

The colour of compounds of transition metals is due to crystal field splitting.



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Question

Do transition metals have high or low melting and boiling points?



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Answer

High melting and boiling points



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Question

What is enthalpy of atomisation?



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Answer

The enthalpy of atomisation is the enthalpy change involved in breaking the metallic lattice of the crystalline metal into individual atoms.



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Question

Does the ionisation enthalpy increase or decrease across a period?



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Answer

The ionization enthalpy gradually increases with an increase in atomic number along a given transition series (though some irregularities are observed). 



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Question

What are the most common oxidation states of Fe?



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Answer

Fe2+, Fe3+



Show question

Question

What is a catalyst?

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Answer

A catalyst is a substance that increases the rate of a chemical reaction without being changed in chemical composition or amount.

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Question

What is a heterogeneous catalyst?

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Answer

A heterogeneous catalyst is in a different phase from the reactants. The reaction occurs at active sites on the catalyst surface.

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Question

Which catalyst is used in the Haber process?

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Answer

Zinc

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Question

The Haber and Contact processes are examples of what type of catalysis?

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Answer

Heterogeneous catalysis

Show question

Question

What are the steps of surface adsorption theory?

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Answer

  1. Adsorption: the reactants stick to active sites of the catalyst surface.
  2. Reaction: the reaction takes place while the reactants are attached to the active sites.
  3. Desorption: the products detach from the catalyst surface.

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Question

What is a homogeneous catalyst?

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Answer

A homogeneous catalyst is in the same phase as the reactants.

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