S orbital contains only 2 electrons and not elements.

Orbitals don't contain elements. The elements each have specific orbitals based on the number of electrons it has. All of the elements have at least one s orbital. Hydrogen being the simplest element has one electron in the 1s orbital. The s orbital can contain a maximum of 2 electrons.

The elements which falls under the group 16 has 4 electrons in its outer p orbital...

Typical transition elements are those elements in which d orbital is in the process of completion.d orbital can occupy 10 electrons. if in any element d orbital contain less than 10 electron it means it has incomplete d orbital and d orbital is in the process of completion. for example Sc has electronic configuration 3d1 4s2. it has 1 e in d orbital. so Sc is typical transition elements.

Cesium