Physical Properties of Transition Elements (HL) (HL IB Chemistry)

What are transition metals?

• The definition of a transition metal is an element with an incomplete d-subshell or an element that can form at least one stable cation with an incomplete d-subshell
• This definition distinguishes them from d-block elements because scandium and zinc do not fit the definition
  • Scandium only forms the ion Sc³⁺, configuration [Ar] 3d⁰
  • Zinc only forms the ion Zn²⁺, configuration [Ar] 3d¹⁰
• The elements of the first transition series are therefore titanium to copper

Where are transition metals on the Periodic Table?

• The transition metals are located in the d-block
  • Period 4: From titanium to copper
  • Period 5: From zirconium to silver
  • Periods 6 and 7 are complicated by the presence of the f-block lanthanides and actinides 

Location of transition metals in the Periodic Table

The transition elements and the d-block elements

Structure and properties of transition metals

• Like other metals, transition metals have a metallic lattice structure
  • Layers of positive ions within a sea of delocalised electrons
• Since the 3d and 4s subshells are so close in energy, the transition metals are able to delocalise their d-electrons to form metallic bonds
• This causes transition metals to have particularly good electrical conductivity and high melting points

Why do transition metals have high melting points?

• The ability to delocalise the d-electrons means that transition metals have a greater electron density
  • This means that the electrostatic forces of attraction between the large positive charge of the cations and the sea of delocalised electrons are strengthened
  • The stronger forces of attraction result in a higher melting point as more energy is required to overcome them
• The melting points of s-block metals range from 27 ^oC for francium to 839 ^oC for calcium 
  • As the following graph shows, all of the Period 4 transition metals have higher melting points than Group 1 and Group 2 metals
  • There is an exception to the lower melting points of s-block metals with a melting point of 1,287 ^oC for beryllium, due to the small size of a beryllium atom resulting in strong metallic bonding 

Melting point graph

 

The Period 4 transition metals have higher melting points than s-block metals

Why do transition metals have high electrical conductivity?

• Transition metals have a large number of delocalised electrons
• Therefore, more electrons are able to move when a potential difference is applied
• This causes transition metals to have high electrical conductivity
• The three most conductive metals are: 
  1. Silver
  2. Copper - the most used metal in electrical cables due to a combination of cost and conductivity
  3. Gold

 

• For more information about other characteristic properties of transition metals, see our revision note on the Characteristic Properties of Transition Elements