Question

Fill in the blanks:
      __________ period is incomplete.

Answer 1

Hint: The Periodic Table, also referred to as the Periodic Element Table, is a tabular show of chemical elements grouped by atomic number, arrangement of electrons, and repeating chemical properties. The table structure reveals periodic tendencies. We need to consider the periodic table as it does not have complete elements and we also need to consider its functions to find out the correct period.

Complete step by step answer:
Let’s discuss a periodic table which is an arrangement of chemical elements in order of their atomic numbers, electronic configuration and repeated chemical properties. In the periodic table the elements are arranged in the order of their increasing atomic number.
The periodic table has its standard form of the table which consists of rows and columns forming grids where rows are referred to as periods and columns as groups.
As we all know that periodic table is the result of two centuries evolution in the understanding of the chemical and physical properties of the elements with the great contribution made by scientists Antoine-Laurent de Lavoisier, Johann Wolfgang Dӧbereiner, John Newlands, Julius Lothar Mere, Dmitri Mendeleev, Glenn T. Seaborg and other too.
$7th$ period in the periodic table is considered as incomplete because it consists of elements which have not been studied properly yet, when we discuss their properties so they may change after getting sufficient information about them. That is why we can't give them permanent recognition in periodic tables whereas all the elements in the periodic table have many properties and similarities to follow to each other. In $7th$ period we've assigned names to some of them and most of them have been artificially synthesized in the laboratory and are not naturally occurring elements. And when we talk about their chemical properties, they are highly unstable elements and not much information is available on them.

Note: While there are elements in nature that we have not yet produced or discovered, scientists already know what they are going to be and can predict their properties.
The seventh period contains elements where it begins with francium and ends with oganesson and the heaviest element currently discovered falls in this period only.