Arsenic compounds are poisonous. Selenium is used in solar cells and light detectors. Krypton is an inert gas used in lasers. Rubidium is used in solar cells and light detectors. Strontium is used in red fireworks.
Yttrium is used in red phosphors in televisions.
Zirconium is in the gems called zircons. Niobium is used in superconductors in magnetic levitation trains. Molybdenum steel is hard when hot and is used in cutting tools. Technetium is radioactive and never occurs in nature. It is used as a radioactive tracer element in the bloodstream to diagnose heart disease.