Lesson one attempts of elements classification

The number of elements in Mendeleev’s periodic table is …….. elements

The scientist who left spaces in his table to be filledwith suitable discovered elements in future is ……

Mendeleev classified the elements of each group into ….. subgroups

The nucleus of the atom contains………..

The scientist who discovered that the nucleus of atom contains positivity charged protons is …..

The scientist ……..had discovered the main energy levels

The number of energy levels in the heaviest known atom is …… levels

The modern periodic table consists of…..horizontal periods

The number of elements which exist in nature is….

The transitional elements start to appear from the beginning of the….period

If the atomic number of an element is 15 so its group is located in ….. block

Nobel gases are located in group …..

In the periodic table the elements which are identical in properties lie in the same …..

The atomic number of an element that exists in group 7A and period 2 is ….

The element whose atomic number 18 is …..