Technetium

Technetium is atom number 43 — every Technetium atom has exactly 43 protons in its center, and that number is what makes it Technetium and nothing else. Its symbol is Tc. At room temperature it is a solid.

Technetium (/tɛkˈniːʃiəm/) is a chemical element with symbol Tc and atomic number 43. It is the element with the lowest atomic number in the periodic table that has no stable isotopes:every form of it is radioactive. Nearly all technetium is produced synthetically, and only minute amounts are found in nature.

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

Technetium sits in period 5, group 7 of the d-block. Its 43 electrons fill shells of 2, 8, 18, 13, 2 — written as [Kr] 4d5 5s2. Its electronegativity is 1.9 on the Pauling scale, and pulling the first electron off takes 702 kJ/mol. The outermost shell holds 2 electrons — the ones that do all the chemistry.

Full configuration: 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d5
Ionization energies (kJ/mol): 702, 1470, 2850
Electron affinity: 53 kJ/mol · Electronegativity (Pauling): 1.9
Density: 11 g/cm³ · melts 2430 K · boils 4538 K

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