Chemistry · Ch 9 — d and f Block Elements
Introduction to d- and f-Block Elements
Introduction to d- and f-Block Elements
The elements in the long middle stretch of the periodic table -- Groups 3 to 12 -- together with the two 14-element rows conventionally shown below the main table, form what is called the transition and inner-transition chemistry of the periodic table. The d-block elements (Groups 3-12) are called transition elements because, as originally defined, they represent a transition in properties between the strongly electropositive s-block metals and the much less metallic p-block elements. The f-block elements, split into the lanthanoids (following lanthanum) and the actinoids (following actinium), are often called the inner-transition elements, since the electron that distinguishes one member from the next is added to an inner f subshell rather than to the outermost shell.
What unites all of these elements chemically is a single structural fact: each has, in the free atom or in at least one of its common oxidation states, a partially filled set of d or f orbitals. It is this partial filling -- not simply "being a metal in the middle of the table" -- that is responsible for essentially every distinctive property covered in this chapter: the existence of multiple stable oxidation states for a single element, the often-vivid colours of their compounds, their effectiveness as catalysts in some of the most important industrial processes, and their paramagnetism.
This chapter (as prescribed by the WBCHSE Semester IV syllabus) develops these ideas for the first-row (3d) transition metals in detail: their general electronic configuration and its exceptions, their occurrence, and the periodic trends in ionic radii, ionization enthalpy, oxidation states, colour, catalytic property and magnetic property across the series from scandium to zinc. It then examines two of the most important and most heavily used transition-metal compounds in the laboratory and in industry, potassium dichromate () and potassium permanganate (), covering how each is manufactured and how each behaves as an oxidizing agent.
The second half of the chapter turns to the inner-transition elements. It covers the electronic configuration, oxidation states, chemical reactivity and uses of the lanthanoids, together with the single most distinctive periodic phenomenon associated with them -- lanthanoid contraction -- and its far-reaching consequences for the chemistry of the elements that follow. It closes with a parallel, comparative treatment of the actinoids: their electronic configuration, their markedly wider range of oxidation states, how they differ from the lanthanoids, and their principal uses, most notably as nuclear fuel.
Taken together, these two related but distinct families -- the d-block transition metals and the f-block inner-transition elements -- account for a disproportionately large share of the periodic table's chemical richness, from the steel and titanium alloys of heavy industry, through the catalysts that make ammonia and sulfuric acid manufacture possible, to the permanent magnets and nuclear fuels of modern technology.