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.

... and commutative
multiplication distributes over addition
|X||Y| + |Z| = |X||Y| x |X||Z|
|X||Y| x |Z| = (|X||Y|)|Z|
The addition and multiplication o ...