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 ...

In fact, when his periodic system was first published, group 7 was rather unique because it contained only one element known at the time — manganese — and had at least two gaps below it.

Group 7 of the periodic table is something of an oddity. When the first periodic table was formulated by Mendeleev, it was the only group that contained just a single known element — manganese.

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 ...