Final answer:
Einsteinium is a synthetic, metallic, highly radioactive element with the symbol Es, atomic number 99, and most stable isotope with an atomic mass of [252]. It is a member of the actinide series, discovered in hydrogen bomb debris, and used mainly in scientific research.
Step-by-step explanation:
Einsteinium is a synthetic element with the atomic number 99 and the symbol Es. It was discovered as a component of the debris of the first hydrogen bomb explosion in 1952, and named after Albert Einstein. Einsteinium is a member of the actinide series and its most stable isotope is Einsteinium-252 with a half-life of about 471.7 days. With an atomic mass of [252], einsteinium's properties are typical of a late actinide, displaying a metallic appearance and radioactive characteristics.
Its position in the periodic table is among the 'transuranium' elements, which are those with atomic numbers greater than that of uranium (92). The standard electron configuration for Einsteinium is [Rn]5f¹117s², indicating that it has an atomic number of 99. Einsteinium is highly radioactive and has mostly been used in scientific research rather than practical applications. Due to its rarity and radioactivity, it requires special handling and precautions in the laboratory.