Einsteinium

Einsteinium is atom number 99 — every Einsteinium atom has exactly 99 protons in its center, and that number is what makes it Einsteinium and nothing else. Its symbol is Es. At room temperature it is a solid.

Einsteinium is a synthetic element with symbol Es and atomic number 99. It is the seventh transuranic element, and an actinide. Einsteinium was discovered as a component of the debris of the first hydrogen bomb explosion in 1952, and named after Albert Einstein.

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

Einsteinium sits in period 7, group 3 of the f-block. Its 99 electrons fill shells of 2, 8, 18, 32, 29, 8, 2 — written as [Rn] 5f11 7s2. Its electronegativity is 1.3 on the Pauling scale, and pulling the first electron off takes 619 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 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f11
Ionization energies (kJ/mol): 619
Electron affinity: -28.6 kJ/mol · Electronegativity (Pauling): 1.3
Density: 8.84 g/cm³ · melts 1133 K · boils 1269 K

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