Noble Gases In The First 20 Elements Of Atomic Table. Noble gases are also called inert gases. Noble gases are present in the 18th group of atomic tables. They are known to be extremely non-reactive.

The periodic table’s arrangement also allows scientists to discern trends in element properties, including electronegativity, ionization energy, and atomic radius. Many scientists worked on the ...

Atoms of the same element with different numbers of neutrons are called isotopes of that element. The atomic mass in the periodic table is an average of the atomic mass of the isotopes of an element.

Atomic Radius: Decreases across a period and increases down a group. ... The first 20 elements of the periodic table are as follows: H – Hydrogen, He – Helium, Li ...

Elements are arranged in the periodic table in order of increasing atomic number. For example hydrogen has the atomic number of one, ... (only true for the first 20 elements).