D-block (for diffuse) elements consist of the transition metals (group 3-12 on the periodic table) in which the outermost electron shell is the D orbital. D-block elements form at least one stable ion with an incompletely filled electron subshell.
... by Paul Buhle: Nonviolent Activist.
1999, May 01 - "Annual Dinner And Peace Award Ceremony: A Celebration Of David McReynolds" - Pamphlet: War Resisters ...