Short answers, pulled from the story.
The identity of a chemical element is determined by the specific count of protons in its nucleus. This atomic number is the fundamental definition that distinguishes one element from another regardless of neutron count or behavior.
The first elements formed in the universe during the first twenty minutes after the Big Bang. Hydrogen and helium were forged in a ratio of roughly three to one by mass, with tiny traces of lithium and beryllium appearing as fleeting sparks.
Dmitri Mendeleev published the first recognizable periodic table in 1869. He arranged elements by increasing atomic weight and left gaps to predict the existence and properties of undiscovered elements like gallium.
Isotopes of the same element have different numbers of neutrons while maintaining the same number of protons. This variation affects their mass and stability, with some isotopes being radioactive and decaying over time.
The heaviest element oganesson was officially recognized in 2016. This discovery completed the seventh row of the periodic table and marked a significant milestone in the global effort to synthesize new elements.
Jöns Jacob Berzelius invented the modern system of chemical symbols in 1814. He used letters from the Latin names of the elements to create a universal language that allows scientists from different countries to communicate effectively.