Answer:

1. He arranged the elements in eight groups but left no gaps for undiscovered elements.

2. Scientists in Japan, the United States and Russia have officially discovered four new elements, at last completing that gap-toothed seventh row of the periodic table and, as the Guardian artfully describes, "rendering science textbooks around the world instantly out of date."

3. You can see a simple version of the modern periodic table in the Figure below. The modern table is based on Mendeleev's table, except the modern table arranges the elements by increasing atomic number instead of atomic mass. Atomic number is the number of protons in an atom, and this number is unique for each element.

4. Iodine has a lower relative atomic mass than tellurium. So iodine should be placed before tellurium in Mendeleev's tables. However, iodine has similar chemical properties to chlorine and bromine. To make iodine line up with chlorine and bromine in his table, Mendeleev swapped the positions of iodine and tellurium.

5.By looking at the chemical properties and physical properties of the elements next to a gap, he could also predict the properties of these undiscovered elements. For example, Mendeleev predicted the existence of 'eka-silicon', which would fit into a gap next to silicon. The element germanium was discovered later.

6.The modern periodic table is used to organize all the known elements. Elements are arranged in the table by increasing atomic number. In the modern periodic table, each element is represented by its chemical symbol. The number above each symbol is its atomic number.

7.this will belong to group 4 because it is capable of forming  four bonds with Cl just like carbon

Explanation: