Q2->They all form acids when combined with hydrogen. They are all fairly toxic. They readily combine with metals to form salts.
Q3->Because their outermost orbit is complete. In Mendeleev's original periodic table there was no place reserved for noble gas. They were discovered in end of 19th century. So Mendeleev created zero group without disturbing original periodic table.
After Louis XVI was executed, Maximilien Robespierre led the Committee of Public Safety in carrying out what became known as the <span>Reign of Terror.</span>
