What element on the periodic table has a mass number of 155 and 99 for the number of electrons

The difference between the atomic number of an element and the element’s atomic mass is the number of ions.

About 70 percent of the earth's surface is water-covered, and about 96.5 percent of all earth's water is salt water. identify the watery feature on earth that is made of freshwater rather than salt water. a) bay b) glacier c) ocean d) sea it is not incomplete this is the true question

Name the element in group 17, period 2. (periodic table)