Development of the Periodic Table Flashcards
Atomic Structure and the Periodic Table (11 cards)
How were elements arranged in the Early 1800s?
By atomic weight and physical and chemical properties
Scientists had no concept of atomic structure or atomic numbers at that time.
What did scientists measure to categorize elements before understanding atomic structure?
Atomic weight
Atomic number was not known until the 20th century.
What periodic pattern was noticed when elements were arranged by atomic weight?
A periodic pattern in the properties of the elements
This pattern led to the name ‘periodic table’.
Who developed a more refined periodic table in 1889?
Dmitri Mendeleev
He arranged 50 known elements into his Table of Elements.
What did Mendeleev do differently when arranging elements in his periodic table?
He arranged elements mainly by atomic weight but switched the order based on properties
This flexibility helped correct earlier misplacements.
Why did Mendeleev leave gaps in his periodic table?
To ensure elements with similar properties stayed in the same groups and to indicate undiscovered elements
These gaps allowed him to predict properties of future elements.
What is an example of Mendeleev’s successful prediction?
He predicted the properties of an element he called ekasilicon, known today as germanium
This prediction was confirmed when germanium was discovered.
What discovery in the early 20th century confirmed Mendeleev’s approach to the periodic table?
The discovery of isotopes
Isotopes have different masses but share the same chemical properties.
True or False: Early periodic tables were complete and accurately categorized all elements.
False
Early tables had elements placed in the wrong groups due to reliance solely on atomic weight.
Fill in the blank: Mendeleev’s periodic table allowed him to predict the existence of _______.
Undiscovered elements
These predictions were based on gaps left in the table.
What element did iodine get placed after in Mendeleev’s table despite having a smaller atomic weight?
Tellurium
Iodine was placed after tellurium due to similar properties.
