Chlorine is more reactive than the iodine in potassium iodide solution: When a Group 7 element reacts, it gains one electron to form a negative ion with a stable electronic configuration – a full ...

The 40th anniversary of the Challenger explosion stirs the memories of Long Island educators who watched the disaster on classroom TVs. Get the latest news and more great videos at NewsdayTV Credit: ...

They could see that relative atomic masses of the elements increased by steps. Many elements were unknown, so these early tables were incomplete. They also contained errors – some elements that were ...