How does a scientist know where on the periodic table to put a newly discovered element?

Explanation:

Periodic table has vertical columns and horizontals rows.

Periods:  The horizontal rows are named as periods in a periodic table.In a period elements with same numbers of principle quantum number ('n') or total number of shells (energy levels) are present. For example : Sodium comes in third period which means that sodium has three shells in total.

Groups: The vertical columns are named as group in a periodic table. In a group elements with same number electrons in their outermost shell are present. For example: In group one all the elements Li, Na, K etc have same number of valence electrons in their outermost shell.

So, in order to place a newly discovered element in a periodic table scientist must have the information regarding the number of valence electrons and total number of shells present in an atom of that element. One can easily look for valence number of electrons and total number of shells from the atomic number of that particular element.

By the knowledge of valence electrons and total number of shells the scientist will able to decide the group number and period number for newly discovered element.

  the   balanced   equation   for   reaction of   ca metal   with   o2 to   produce   cao   is as below

2 ca+ o2→ 2 cao2

  explanation

the reaction is   balanced     since the   number of atoms   in reactant side is   equal to   number of atoms   in   product side.   for   example   they   are 2   atom of   ca in   reactant   side   and   2   atoms of ca   in   the product side.

  the   process   is a   meet the   requirement   of   redox   reaction because :     calcium   is   oxidized   from   oxidation state 0   to 2+   while   oxygen   is reduced from   oxidation   state   0   to 2-