A transition metal (also known as a transition element) is a chemical element that, either in its elemental form or as an ion in compounds, has a partially full d subshell, allowing the d orbitals to participate in chemical bonding. The periodic table's d-block, which is a criteria commonly used to define them, roughly corresponds to the elements in the transition metals. The phrase "transition metal" has several different definitions, but is often used to refer to all elements in groups 4 through 11, as well as scandium and yttrium from group 3. Additionally, they frequently include lutetium and lawrencium or lanthanum and actinium. Sometimes referred to as inner transition metals, the lanthanide and actinide series of the f-block are in fact transition metals. They have high electrical and thermal conductivity and are glossy.