Patients who waited more than 6 months to receive cataract surgery experienced more vision loss, a reduced quality of life and had an increased rate of falls compared with patients who had wait times of less than 6 weeks.
The chalcogens, the oxygen group, is located in column 16 of the periodic table. It contains the elements oxygen, sulfur, selenium, tellurium, polonium, and ununhexium (O, S, Se, Te, Po, and Uuh, respectively). These elements all contain six valence electrons and form 2- ions.
The group number of an element in the periodic table is the same as the number of electrons in its outer shell. An element in group 1 has 1 electron in its outer shell. An element in group 2 has 2 electrons in its outer shell. An element in group 7 has 7 electrons in its outer shell. An element in group 0 has a full outer shell. The number of electrons in the outer shell gives the element its chemical properties and controls its chemical reactions.