sentences: chlorine is a kind of element & sodium is a kind of element ->  sodium and chlorine are two elements  sodium and chlorine are two elements & sodium chloride is always made of chemically combined chlorine and sodium ->  sodium chloride is made of two elements chemically combined  sodium chloride is made of two elements chemically combined & a compound is made of two or more elements chemically combined ->  sodium chloride is a compound  sodium chloride is a compound & sodium and chlorine reacting forms sodium chloride -> sodium and chlorine reacting forms a compound