C3aL5 Trends 3: The Transition Metals
Key Words
Electron arrangement - arrangement of electrons in the shells.
Shell - a region around the atom where it is most likely that an electron will be found.
Transition Metals - elements in the periodic table found between Group II and Group III
Grade E
The transition metals are found between Groups II and II of the periodic table. They have typical metal properties:
- Strong;
- Shiny;
- Hard;
- Good conductors;
- High density.
Their chemical properties have different patterns that do not enable them to fit in easily with particular groups. Transition metals are generally (but not exclusively) not very reactive. Mercury is a liquid at room temperature, having a melting point of -33 oC.
Grade C
We have stated that the maximum number of electrons in the outer shell is eight. With the transition metals the shell that is one in from the outer shell can hold up to a maximum of 18 or 32 electrons. We can look at the electronic arrangements of a number of transition metals:
| Element | Symbol | Atomic Number | Electronic Arrangement |
| Iron | Fe | 26 | 2 - 8 - 14 - 2 |
| Cobalt | Co | 27 | 2 - 8 - 15 - 2 |
| Nickel | Ni | 28 | 2 - 8 - 16 - 2 |
| Copper | Cu | 29 | 2 - 8 - 17 - 2 |
| Zinc | Zn | 30 | 2 - 8 - 18 - 2 |
The outer shell is full with two electrons, but the second to outermost shell fills with electrons, until it is completely full with electrons.
That is not the only thing that is strange; the second to outer shell can donate or accept electrons.
The melting points and boiling points are much higher than those of the alkali metals:
| Element | MP oC | BP oC | Density g/cm-3 |
| Iron | 1538 | 2681 | 7.87 |
| Cobalt | 1495 | 2927 | 8.90 |
| Nickel | 1453 | 2732 | 8.91 |
| Copper | 1084 | 2562 | 8.94 |
| Zinc | 420 | 907 | 7.13 |
Since there are a lot more electron shells, the transition metals do not lose or gain electrons that easily. Therefore they are less reactive than the alkali metals.
Grade A
The compounds of transition metals tend to have distinctive colours. When light is shone onto the material, an unpaired electron is taken from the second to outermost shell to the outer shell. The atom is excited, which means it has excess energy. Then the electron drops back down. The light given off depends on the energy that is given out as the electron drops. The light is given out as a tiny packet of light called a photon.
