Timeline of The Periodic Table Flashcards
In 1817, what did Jobann Dobereiner spot? What did he do?
He spotted that the same elements shared similar propertiesc and began putting them into Groups of 3 called Triads
What did Johann also notice?
The atomic weights of the middle element was approximately the average of the atomic weights of the top and bottem element
Why was Johann’s theory abandoned?
As new elements were discovered it was difficult to fit them into triads, so his new theory only particularly worked
In what year and who arranged the known elements in order of increasing atomic weights? What did he find? What did he call it?
In 1864, John newlands - he found similar properties amongst every 8th element and called it the law of octaves
What else did Newlands notice?what did he not do?
He noticed that some patterns were repeated, he didnt leave any gaps for undiscovered elements so this upset the order
What happened to the elements in newlands order?
Some ended up in the wrong place and some ended up occupying the same spot
What and which year did Mendeleev create a table?
In 1869, he created a periodic table based on atomic weights like Newlands but mendleevs left gaps
What did Mendleev’s periodic table enable him to do?
To predict the existence of undiscovered elements, and to group elements with similar properties.
What is the modern periodic table like?
The table is rearranged in order of atomic number due to the discovery proton, neutron and electron.
Where do the metals appear on the modern table and where do the non metals appear?
Metals - appear on the left towards the bottem
Non - metals - right of the table
What is the modern table more accurately described as? And why?
Described as an arrangement of the elements in order of electronic structure.
It is like this as in a neutral atom the number or protons = the number of protons
