The Periodic Table Flashcards
What four elements did Greek philosophers think were part of what the world was made up of
Fire, earth, water, air
What’s Roberts Boyles contribution to the Periodic table?
Defined an element
Defined compounds
What is an element
A substance that cannot be broken into simpler substances by chemical means
What was Humphry Davy’s contribution to the periodic table?
Discovered potassium by passing electricity through a compound of potassium, which showed elements cold be extracted from their compounds using electricity.
Also discovered sodium, calcium, barium, strontium and magnesium the same way
What are Dobereiner’s Triads?
A triad is a group of three elements with similar chemical properties, where the atomic weight of the middle element is equal to the average of the other two.
Name examples of triads
Chlorine Bromine Iodine
Calcium Strontium Barium
Lithium Sodium Potassium
What is are Newlands’ Octaves
They are arrangements of elements in which the first and the eight element, counting from a particular element, have similar properties
What were some problems with Newlands’ Octaves?
Some elements weren’t discovered yet, Newland should have left gaps
Noble gases weren’t discovered yet
What is Mendeleev’s Periodic Law
When elements are arranged in order of increasing atomic weight, the properties of the element recur periodically
Summarise Mendeleev’s work
Placed elements with similar properties in the same vertical column to demonstrate the regular repetition of properties.
Left gaps in Table, to make all known elements fit into the proper group.
Predicted the properties of undiscovered elements, since he knew the properties of the other elements in that group
Reversed the order of some elements to make them fall into groups of elements with similar chemical properties
What is an atomic number
Number of protons in nucleus of atom
Moseley’s contribution to Mendeleev’s table
Used X-rays to find atomic number of an element
Showed if elements are arranged in order of increasing atomic number it is not necessary to reverse them
Moseley’s X-ray study proved Mendeleev right for putting tellurium above iodine, despite the higher atomic weight of tellurium
Showed that by arranging them in order of increasing atomic number the elements fall into the correct groups naturally
What is the Modern Periodic Law
When Elements are arranged in order of increasing atomic number, the properties of the element recur periodically
What are the differences between Mendeleev’s Periodic table and the Modern one?
Mendeleev’s is arranged in order of atomic weight while the modern periodic table is order of increasing atomic number
More elements in modern periodic table, cause some elements were not discovered like noble gases
No gaps in Modern Periodic Table
Transition elements are listed in a separate block in the middle of the table in the Modern Periodic table
What is mass number
The sum of number of protons and neutrons in nucleus of element
