Organising the Elements
How many elements had scientists discovered by 1860?
Scientists had discovered around 60 elements.
Who was Dmitri Mendeleev?
He was a Russian scientist who developed the first periodic table.
Which element was discovered in 1874?
Gallium was discovered in 1874.
How much rhenium was extracted from 660 kg of rock?
They extracted only 1 gram of rhenium.
What did scientists want to find out about the elements?
They wanted to find patterns in the properties of elements and discover new elements.
How did Mendeleev organise the elements?
He arranged the elements in order of atomic mass and grouped elements with similar properties together.
Who discovered gallium?
A French scientist discovered gallium.
What did the discoveries of the missing elements prove?
They proved that Mendeleev's predictions were correct.
What did John Dalton study in the early 1800s?
He studied evidence from experiments and suggested that atoms of each element have a different mass.
What information did Mendeleev write on each card?
He wrote the name of the element, its atomic mass and its properties.
Which two elements were discovered by Swedish scientists?
Scandium and germanium.
Why was Mendeleev’s periodic table important?
It organised the elements and helped scientists predict undiscovered elements.
What did Stanislao Cannizzaro work on?
He worked on the masses of atoms.
Why did Mendeleev leave gaps in his periodic table?
He left gaps for elements that he predicted existed but had not yet been discovered.
What were the properties of scandium and germanium?
Their properties were as Mendeleev had predicted.
Why did scientists use atomic mass to organise the elements?
They used atomic mass to find patterns in the properties of elements.
What happened at the conference in Germany in 1860?
Cannizzaro gave data about the masses of atoms of the elements.
What did Mendeleev predict about undiscovered elements?
He predicted their properties.
Who discovered rhenium?
Ida Tacke and Walter Noddack discovered rhenium.
How did other scientists help Mendeleev develop the periodic table?
They provided data about the properties and atomic masses of elements.