Chemistry · Ch 4 — The d- and f-Block Elements
Introduction
Introduction
The d-Block and the f-Block
The periodic table sets aside two large blocks of elements for atoms whose distinguishing feature is that new electrons enter an inner orbital rather than the outermost shell. The d-block spans groups 3 to 12 — the wide middle stretch of the table — and its elements are progressively filling their d orbitals. The f-block sits apart, in the two rows conventionally printed below the main table, and its elements are progressively filling their 4f or 5f orbitals. Because of where these fills occur, d-block elements are commonly called transition metals and f-block elements are called inner transition metals.
Four Transition Series and Two Inner Transition Series
Each of the four periods that contain d-block elements produces its own horizontal row, or series, of transition metals:
- 3d series — Sc to Zn
- 4d series — Y to Cd
- 5d series — La, then Hf to Hg
- 6d series — Ac, then the elements from Rf to Cn (mostly synthetic, short-lived)
The f-block similarly splits into two series:
- 4f series (lanthanoids) — Ce to Lu
- 5f series (actinoids) — Th to Lr
A "series" is simply the run of elements across a period over which a particular d or f sub-shell is being filled, one electron at a time, as the atomic number increases.
What Actually Counts as a "Transition" Element — the IUPAC Test
The label "transition" is historical: these metals were first singled out because their chemical behaviour seemed to sit between that of the s-block and p-block elements on either side of them. IUPAC has since sharpened this into a precise test — an element is a transition metal if it has an incompletely filled d sub-shell, either in its neutral atom or in at least one of the common ions it forms.
This is why zinc, cadmium, and mercury (group 12) are usually excluded from the strict definition: each has a completely filled configuration in its ground state and in every oxidation state it commonly adopts, so none of them ever has an incomplete d sub-shell. Even so, because they are the final members of the 3d, 4d, and 5d series respectively, their chemistry is conventionally studied together with that of the true transition metals.
Why This Unit Matters
Several of the most familiar metals in human history and industry come straight out of this part of the periodic table — iron, copper, silver, and gold among them — and their properties have shaped metallurgy, currency, and technology for millennia. The inner transition metals matter for a very different reason today: elements such as thorium, protactinium, and uranium are central to modern nuclear power generation.
How This Unit Is Organised
The unit first works through the d-block: electronic configuration, natural occurrence, and the general characteristics and periodic trends of the transition metals, with particular attention to the first (3d) row, along with the preparation and properties of two industrially important compounds, potassium dichromate and potassium permanganate. It then turns to the f-block, covering the electronic configurations, oxidation states, and chemical reactivity of the inner transition metals.