Which of these pairs of elements have the same number of valence electrons?
hydrogen (h) and helium (he)
sodium (na) and potassium (k)
carbon (c) and oxygen (o)
boron (b) and beryllium (be)

In a modern periodic table, there are seven periods. a period is any horizontal row of the periodic table, and the elements in a period have consecutive atomic numbers. a group is any vertical column in the periodic table, and there are 18 such groups. groups 3–12, also known as the “b” group elements, are called transition metals. groups 1–2 and 13–18, also known as the “a” group elements, are sometimes called the main groups. metals are characterized by malleability, ductility, conductivity, and a tendency to lose electrons. main group metals are found in groups 1 and 2. nonmetallic elements fall on the right-hand side of the periodic table, that is, groups 13–18. nonmetals have the tendency to gain electrons and are generally brittle. they can be solids, liquids, or gasses at room temperature. now, label the areas of the modern periodic table using the above information. drag the appropriate labels to their respective targets.