Mendeleev’s principle of chemical periodicity states that when the elements are arranged according to their atomic numbers. this periodic law allows elements with similar properties to appear at regular intervals. predict the group of elements and their number of valence electrons that will combine in a 2: 1 ratio to with sodium. a) bromine, chlorine, iodine, 7 b) sulfur, selenium, polonium, 6 c) hydrogen, fluorine, potassium, 1 d) calcium, phosphorus, tellurium, 2

Which type of bond is present in hydrogen sulfide (h2s)? the table of electronegativities is given. a. hydrogen b. ionic c. nonpolar covalent d. polar covalent

This question is about electrolysis. metal spoons can be coated with silver. this is called electroplating. suggest one reason why spoons are electroplated?

Problem page combustion of hydrocarbons such as pentane ( c5 h12 ) produces carbon dioxide, a "greenhouse gas." greenhouse gases in the earth's atmosphere can trap the sun's heat, raising the average temperature of the earth. for this reason there has been a great deal of international discussion about whether to regulate the production of carbon dioxide.(a) write a balanced chemical equation, including physical state symbols, for the combustion of liquid pentane into gaseous carbon dioxide and gaseous water. (b) suppose 0.350 kg of pentane are burned in air at a pressure of exactly 1 atm and a temperature of 20.0 degree c. calculate the volume of carbon dioxide gas that is produced. be sure your answer has the correct number of significant digits.