history of the periodic table Flashcards
How did Dimitri Mendeleev arrange the periodic table
- He left gaps
- he mainly ordered elements in increasing atomic weight
- he arranged elements that had similar properties into rows and columns
how are elements grouped
by chemical properties
how is the periodic table arranged (modern times)
- in order of atomic number
- patterns of chemical and physical properties (groups and periods)
how was the periodic table arranged in the earlier times
in order of atomic weight
why do we use the word ‘periodic’ in the periodic table
because scientists noticed a periodic pattern in the properties of the elements (e.g. a pattern that repeats)
why were elements often placed in the wrong group in early versions of the periodic table
elements were placed in order of atomic weight rather than atomic number, and didn’t take into account the chemical properties
why did Dimitri Mendeleev leave gaps in the periodic table
- for unknown elements
- to ensure that elements of similar properties stayed in the same group
How did the discovery of isotopes help to validate Mendeleev’s periodic table
some isotopes had different masses but the same chemical properties - so he was correct in putting them in groups with other elements that had the same chemical properties
what does the group number tell you about the atom of the element
the number of electrons on its outer shell
what does the period tell you about the atom of the element
the number of shells an atom has
what name is given to the elements in group 1
Alkali metals
what name is given to the elements in group 2
Alkali earth metals
what name is given to the elements in group 7
Halogens
what name is given to the elements in group 0
Nobel gases
why did Mendeleev think there must be undiscovered elements?
If the elements known about at the time were placed consecutively, some elements would be placed into groups where they had different chemical properties from the other elements in that group. This meant they would be in the ‘wrong’ group, and so Mendeleev thought some undiscovered element must go in that place instead
What is the modern name for atomic weight?
Relative atomic mass
