At Room Tempeture, Metals contain the most Elemants.
Group 17 (halogens)
group 18
The vertical "groups" group elements by chemical properties the horizontal "periods" group elements by the number of energy levels
Group 18 has noble gases.
Group 3 of the periodic table contains many of the radioactive elements.
Atom number 20 is Calcium (period IV, group 2)
In the periodic table, the elements are arranged by atomic number
Two--mercury and bromine
the halogens
group 18
Group 17 (halogens)
group 18
The halogens, listed in column 17 of a wide form periodic table.
The vertical "groups" group elements by chemical properties the horizontal "periods" group elements by the number of energy levels
Group 18 has noble gases.
Group 3 of the periodic table contains many of the radioactive elements.
Those gases are called noble gases. They are i the 18th group of the periodic table.