An element, its atomic number is 19, so the electronic configuration of its ion is _____

When alkali metal reacts with water, _____ gas evolves.

There are ____ bonds between water molecules

Acidic oxides formed by the reaction of nonmetals with Oxygen

During the water electrolysis by Hoffmann's voltammeter, oxygen gas evolves at the negative cathode

The ionosphere is surrounded by two magnetic belts known as Van-Allen belts

The density of ice is ____ than its density in liquid water

__________ is one of the endangered birds in Egypt

______ is a complete body fossil.