How did Mendeleev resolve conflicts between chemical properties and strict atomic-weight order?
He prioritised chemical properties, changing the order of some elements to place them in groups matching their properties.
AQA GCSE Combined Science: Trilogy (8464) — Chemistry — Higher · 5.1.2.2
Revise AQA GCSE Combined Science: Trilogy (8464) — Chemistry — Higher specification point 5.1.2.2, Development of the periodic table, with free active-recall flashcards. Flip through the set or review every question and answer below.
1 / 12
How did Mendeleev resolve conflicts between chemical properties and strict atomic-weight order?
He prioritised chemical properties, changing the order of some elements to place them in groups matching their properties.
Why did Mendeleev leave gaps in his periodic table?
Patterns in chemical properties suggested that elements were missing, so he left spaces for elements not yet discovered.
What was the main benefit of Mendeleev's approach to arranging elements?
Elements with similar properties lined up more consistently.
How were elements ordered in early periodic tables?
By increasing atomic weight.
What were chemists trying to achieve by ordering elements by atomic weight?
To find a pattern that grouped elements with similar properties.
What pattern did early periodic tables reveal?
A repeating pattern in the properties of elements.
Why did strict atomic-weight order not produce a fully correct periodic table?
It placed some elements in groups that did not match their chemical behaviour.
Why were early periodic tables incomplete?
Not all elements had been discovered.
What could Mendeleev predict from gaps and surrounding patterns in his periodic table?
The existence of undiscovered elements and their likely properties.
Why did later discoveries of elements strengthen acceptance of Mendeleev’s periodic table?
The elements filled gaps and matched his predictions, providing evidence that his arrangement was sound and could predict new chemical knowledge.
What are isotopes?
Atoms of the same element that have different masses.
Why did knowledge of isotopes help justify some of Mendeleev’s departures from strict atomic-weight order?
Elements can be mixtures of isotopes, so their measured atomic weights do not always increase in the correct sequence of elements.