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Chemistry Revision-C1 Part 2-Period Table: (Dimitri Mendalev (Different…
Chemistry Revision-C1 Part 2-Period Table:
Dimitri Mendalev
Arranged elements by atomic mass
Grouped elements according to similarities
With the gaps, he predicted the atomic mass for the elements that weren't discovered yet.
Mendeleev thought he had arranged elements in order of increasing relative atomic mass but this was not always true because of the relative abundance of isotopes of some pairs of elements in the periodic table
Different from modern
Based on atomic mass however now based on atomic number
Didn't include noble gases
Fewer elements
Had gaps
Similarities
Metals are non-metals are separated
Elements are arranged into groups and periods
Similar properties
Elements arranged in order of
increasing atomic number, in rows called periods
Elements with similar properties
are placed in the same vertical columns called groups
Non-metals on left hand side of periodic table and metals on left hand side
Chemical properties
Metals
Few electrons on outer energy levels so lose electrons easily
Non-metals
Most have full out energy levels so they tend to gain electrons
Some have full outer levels
Electronic Configuration
First orbital has up to 2 electrons, the other orbitals have up to 8 electrons
The group the element is in is the same amount of electrons on its outer orbital
Physical properties
Non-metals
Opposite to metals
Most are liquid or gas at room temperature
Metals
Good conductors
Ductile
Malleable
Shiny
Most are solid at room temperature
Period (rows)
Horizontal rows
Periods
Atomic number and mass increases as you move from left to right in a period
All atoms of the elements in the same period have the same number of orbitals/levels
Groups (columns)
Vertical rows
Atomic mass and number increases as you move from top to bottom
Elements in the same groups usually have similar physical and chemical properties
Exceptions
Transition elements (3-12)
Hydrogen
Helium (has 2 valence electrons)
Atoms of elements in the same groups have the same number of electrons in the outer orbitals of their atom
18 groups