He was able to work out the atomic mass of the missing elements, and so predict their properties. And when they were discovered, Mendeleev turned out to be right. For example, he predicted the properties of an undiscovered element that should fit below aluminium in his table. When this element, called gallium, was discovered in 1875, its properties were found to be close to Mendeleev's predictions. Two other predicted elements were later discovered, lending further credit to Mendeleev's table.
In 1869, a Russian scientist named Dmitri Mendeleev arranged the elements in a table according to their atomic mass, this was the first periodic table. However, a few elements didn't fit the pattern in Mendeleev's table, so a new table had to be made, and that table is today's periodic table which is arranged by atomic number, and not atomic mass.
Gallium and germanium were important to Mendeleev because their properties fit well into his periodic table, filling the gaps he had predicted based on the patterns of other elements. The discovery and confirmation of these two elements helped validate his periodic law and strengthen his periodic table's credibility.
Dmitri Mendeleev noticed gaps in the periodic table when he arranged elements by increasing atomic mass and saw that certain elements with similar properties did not fit into the pattern. He predicted the existence and properties of these missing elements based on the trends in the known elements around them.
Yes, Dimitri Mendeleev did (accurately, I might add) predict where elements would appear in his table. He also correctly predicted some of the missing elements' properties, based on where they were positioned in his table.
what did Mendeleev see that elements it into
He was able to work out the atomic mass of the missing elements, and so predict their properties. And when they were discovered, Mendeleev turned out to be right. For example, he predicted the properties of an undiscovered element that should fit below aluminium in his table. When this element, called gallium, was discovered in 1875, its properties were found to be close to Mendeleev's predictions. Two other predicted elements were later discovered, lending further credit to Mendeleev's table.
In 1869, a Russian scientist named Dmitri Mendeleev arranged the elements in a table according to their atomic mass, this was the first periodic table. However, a few elements didn't fit the pattern in Mendeleev's table, so a new table had to be made, and that table is today's periodic table which is arranged by atomic number, and not atomic mass.
Hafnium is an element not a rock. Hafnium is never found in nature pure form so does not fit into any groups. Hafnium is a chemical element, a metal placed in the group 4 and period 6 of the periodic table of Mendeleev.
Gallium and germanium were important to Mendeleev because their properties fit well into his periodic table, filling the gaps he had predicted based on the patterns of other elements. The discovery and confirmation of these two elements helped validate his periodic law and strengthen his periodic table's credibility.
They fit the pattern: element + compound --> different element + different compound. Example: Zn + CuSO4 --> Cu + ZnSO4.
Mendeleev left gaps in his table to place elements not known at the time. 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. Its properties were found to be similar to the predicted ones and confirmed Mendeleev's periodic table.
This is a very wordy response, but by setting up the Periodic Table according to elements' properties and characteristics, he was able to predict any given elements' properties because, with the way the Periodic Table is arranged, all of the elements surrounding any specific element would have similar properties to the element that they surrounded. For example, at the time there was no element known as Aluminum, but given the properties of the elements around that area (Group 13), he was able to correctly predict Aluminum's properties. When aluminum was discovered, Mendeleev's predictions were extremely close to the actual element's properties.
A clear refutation of Mendeleev's predictions would have been discovering elements that did not fit into his periodic table based on atomic weight and properties. If the properties of elements did not repeat in a periodic manner when arranged by atomic weight, this would have refuted his periodic law.
Dmitri Mendeleev and Julius Lothar Meyer independently published there versions of the Periodic Table between 1869 and 1870. Mendeleev's version would become the foundation of the table used today.
Mendeleev was unable to include helium, neon, and argon in his table because they were discovered after his periodic table was published in 1869. These noble gases were isolated much later in the late 19th and early 20th centuries and did not fit into Mendeleev's original classification of elements based on their properties.
electrons