Exposure to a sufficient quantity of ultraviolet will redden the skin, producing erythema - a sunburn. The amount of exposure necessary to produce this reddening depends on the wavelength. For a 1.0cm^2 patch of skin, 3.7 mJ of ultraviolet light at a wavelength of 254nm will produce reddening; at 300nm wavelength, 13mJ are required. Part A What is the photon energy corresponding to each of these wavelengths? E_254, E_300 = ?J

Up of elements with the same number of valence electrons. vertical column in the periodic table of elements such as alkali metals or halogens. a horizontal row of elements in the periodic table. this is a characteristic of the elements in the periodic table that shows a pattern. it may increase or decrease across or down the table. periodic trend these are the highly reactive elements located in group 1 of the periodic table. these elements have one electron in their outer energy level which makes them highly reactive with water and halogens. these are the reactive elements located in group 2 of the periodic table. these elements have two electrons in their outer energy level which makes them reactive with water and halogens. alkaline earth metals these are the group 3 or d-block elements. these dense metals with high boiling points can have different oxidation states and all are solid at room temperature with the exception of mercury. transition metals this is the highly reactive family of elements with 7 valence electrons. this is an element with full valence shell, very unreactive. this is a group of elements with few valence electrons that conducts heat and electricity. one of a class of elements having properties intermediate to metals and nonmetals. this is a type of element that has many valence electrons, not a conductor.