Meitnerium

Meitnerium is atom number 109 — every Meitnerium atom has exactly 109 protons in its center, and that number is what makes it Meitnerium and nothing else. Its symbol is Mt. At room temperature it is a solid.

Meitnerium is a chemical element with symbol Mt and atomic number 109. It is an extremely radioactive synthetic element (an element not found in nature that can be created in a laboratory). The most stable known isotope, meitnerium-278, has a half-life of 7.6 seconds.

Summary from the source dataset, derived from Wikipedia (CC BY-SA 3.0) · original article

Meitnerium sits in period 7, group 9 of the d-block. Its 109 electrons fill shells of 2, 8, 18, 32, 32, 15, 2 — written as *[Rn] 5f14 6d7 7s2. Its electronegativity is — on the Pauling scale. The outermost shell holds 2 electrons — the ones that do all the chemistry.

Full configuration: 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f14 6d7
Electron affinity: — kJ/mol · Electronegativity (Pauling): —
Density: 37.4 g/cm³ · melts — · boils —

Values exactly as published — see where the data comes from.