d-block elements are also called as transition elements.
Transition elements or transition metals
Transition elements are elements with partially filled d orbitals. An element with a partially filled d subshell or the ability to shape stable cations with an incompletely filled d orbital is referred to as a transition element. Any element that corresponds to the d-block of the modern periodic table, which consists of groups 3 to12, is called a transition element.
Since the f-block elements have incompletely filled f-orbitals, they are often referred to as inner transition elements or inner transition metals.
Electronic Configuration of Transition Elements
d-block elements have a general electronic configuration of (n-1)d 1-10ns 1-2. These elements can find stability in half-filled orbitals and completely filled d orbitals.