Supply the missing word from those in brackets: If an element has one electron in it's outermost energy level [shell] then it is likely to be …………… [metallic / non- metallic].

Copy and complete the following sentences choosing the correct word or words from those given in brackets at the end of each sentence :

The similarities in the properties of a group of elements is because they have the same …………… [electronic configurations, number of outer electrons, atomic numbers.]

How many elements are there in Period 2.

What are elements. Give a reason why elements need to be properly classified.