Ключевые слова: alkali metal, atom, atomic, black, button, caution, chemical, chemistry, design, education, electron, element, graphic, icon, illustration, lab, laboratory, mass, material, mendeleev, metal, molecule, name, nature, notification, periodic, periodic table, physics, potassium, primordial, proton, school, science, scientific, sign, square, structure, substance, symbol, system, table, technology, universe, warning, weight, white,