State two differences between Mendeleev's periodic table and the modern periodic table of the elements. - Leaving Cert Chemistry - Question b - 2010
Question b
State two differences between Mendeleev's periodic table and the modern periodic table of the elements.
Worked Solution & Example Answer:State two differences between Mendeleev's periodic table and the modern periodic table of the elements. - Leaving Cert Chemistry - Question b - 2010
Step 1
Arranged in terms of atomic weight
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Answer
Mendeleev's periodic table was primarily arranged according to atomic weight, whereas the modern periodic table is organized based on atomic number, which reflects the number of protons in the nucleus of an atom.
Step 2
Left gaps for undiscovered elements
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Answer
Mendeleev's table included gaps for elements that had not yet been discovered, predicting their existence and properties. In contrast, the modern periodic table does not have gaps for unknown elements, as all currently recognized elements are included, with elements like the lanthanides and actinides categorized in specific blocks.
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