Because they are neither metals nor non-metals
Selenium is a non metal. It belongs to oxygen family or group 16.
Helium is a noble gas. It belongs to group 18
The 3 kinds of elements are metal, non-metals, and metalloids.
The alkaline earth metals are metals!
Strontium is not a metalloid; it is a metal. It belongs to the group 2 elements in the periodic table, also known as the alkaline earth metals. Metalloids have properties that are in between metals and nonmetals, whereas strontium displays typical metallic characteristics.
non-metal
non metal
cesium is in the metalloids group ;0
The elements that form a zigzag line on the periodic table belong to the metalloids group. Metalloids have properties that are intermediate between metals and nonmetals. They typically exhibit characteristics of both groups, such as being semi-conductive and having varying degrees of metallic and non-metallic properties.
metalloids
Oxygen, sulfur, selenium: non metals; probable also ununhexium. Tellurium, polonium: metalloids
Tellurium (Te) is a metalloid. It is a p block element and belongs to group 16