Download Chemical-Periodicity

Chemical Periodicity
History
• Dmitri Mendeleev (1834 – 1907)
– Russian chemist
– Noticed regular (periodic) recurrence of chemical and physical
properties after arranging by increasing atomic mass.
• Eventually led to grouping by similar properties side by side
Predicted properties of then unknown elements with amazing accuracy.
• Henry Mosely (1887 – 1915)
– British physicist
– Identified atomic number (nuclear charge) of the atoms of elements
• Arranged periodic table by atomic number
Current arrangement of periodic table
The Periodic Table
• Periods – horizontal rows of the periodic
table.
• Groups – vertical columns of the periodic
table.
• Periodic Law – when the elements are
arranged in order of increasing atomic
number, there is a periodic pattern in their
physical and chemical properties.
Electron Configuration/Periodicity
1.
Noble gases
–
2.
Outermost p and s sublevels are filled
Representative elements
–
–
Outermost p and s sublevels are only partially filled
Called the Group A elements
1.
2.
3.
3.
Transition metals
–
–
4.
Alkali metals – group 1A
Alkaline earth metals – group 2A
Halogens – group 7A
Outermost s sublevel and the nearby d sublevel contains electrons
Called the group B elements
Inner transition metals
–
Outermost s sublevel and the nearby f sublevel generally contain
electrons
Atomic Radius
• = half the distance between the nuclei of two
like atoms.
• Atomic size generally increases as you move
down a group.
• Atomic size generally decreases as you move
from left to right across a period.
Largest atoms are towards the bottom and to
the left of the periodic table.
Ionization Energy
• = The energy that is required to overcome the
attraction of the nuclear charge and remove
an electron from a gaseous atom.
• Ionization energy decreases as you move
down a group of the periodic table.
• For the representative elements, ionization
energy generally increases as you move from
left to right across a period.
Electronegativity
• = the tendency for the atoms of the element
to attract electrons when they are chemically
combined with another element.
• Electronegativity increases for the
representative elements as you move from
left to right and generally decreases as you
move down a group.