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.
Elements in group Ia are Alkali metals; group IIa the alkaline earth metals; group VIIa the halogens; group 0 the Inert gases. The position of the elements on the periodic table is based on electron structure (which gives the similar properties that have already been described). The period of the table (which horizontal row the element is in) corresponds to the principal quantum number of the elements i.e the number of shells.