In 1869, Mendeleev published his arrangement of the known elements in a “periodic table”. Just over ……..…………… elements were arranged using details of their …………..……… and compounds. This table revealed ………………..… in the chemical properties of elements in the same vertical column.
The elements of the periodic table are arranged in order of ……………..…… atomic number. The atomic number reflects the number of ………………….. in the nucleus of each atom.
Elements are arranged in rows of increasing atomic number called ………..………….
Elements with similar properties are arranged in the same vertical column, called ……………..…….
Metals are grouped on the left and ………..………… of the periodic table.
Gases are positioned on the ……..…………… of the periodic table (except hydrogen).
Semi-metals are grouped between metals and non-metals and have some properties that are ……..…………… to both types of element.
Find the value of the variable, to the nearest tenth.