Elements that lie in the same column on the periodic table (called a group) have identical valance electron configurations and consequently behave in a similar fashion chemically. For instance, all the group 18 elements are inert, or noble gases. Element groups are either nonmetals or various subsets of metals, but there is no distinct line between the two types of elements. Metal elements are usually good conductors of both electricity and heat. Subsets are based on similar characteristics and chemical properties.
3 doctors agreed: A few hours: The typical dilating drops used at most eye doctors last about 4-6 hours. Some individuals are more sensitive to the effects and can remain dilated for up to a day. And if stronger dilating drops were used for a particular reason, their effects could last from 8 to 24 hours. ...Read more.
My eyes are normally dilated ~80% (I never have to get the drops at the optometrist for the back-eye pictures) and even just a little increase in pupil size is just so dang interesting while rolling. If given 5 free minutes and a mirror I will spend 10 minutes staring at my eyes in glee.