Title: PERIODICITY
1PERIODICITY
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3History of the Periodic Table
- 70 elements had been discovered by the
mid-1800s, but until Dmitri Mendeleev, no one
had come up with a way to organize the elements. - Mendeleev came up with the first working system
of filing the elements. - He listed the elements in columns in order of
increasing atomic mass, and then put columns
together that were similar
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5History of the Periodic Table
- Mendeleev left gaps in the table since there were
no current elements that seemed to fit those
spots - Those elements were eventually discovered and
they fit perfectly into an open spot. - The 1st scientist that set the table in order of
atomic number was Henry Moseley
6History of the Periodic Table
- The modern PT is arranged by increasing atomic
number - Increases from left to right, and
top to bottom - This establishes the periodic law
- When the elements are arranged in order of
increasing atomic , there is a periodic
repetition of their phys chem properties
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8Periodic Table 101
- Most of the elements
on the periodic table are metals - 16 of the elements
are classified as nonmetals - There are 7 elements that cant
be classified as metals or nonmetals,
and they are called metalloids. - The noble gases are the last column
on the table and significant because they are
chemically inert
9Periodic Table 101
- There are 2 elements that are liquid at room
temperature (Br Hg). - There are 11 gaseous elements (the
noble gases, H, O, N, F, Cl) - The rest of the elements are solids at room
temperature - Elements 1-92 are naturally occurring with the
exception of Tc, the rest were manufactured with
an atom smasher
10Periodic Table 101
- Hydrogen is the most abundant element in the
universe - Francium is the least abundant natural element
- The most abundant element on earth
is Oxygen - There are over 10,000,000 carbon
compounds - The most reactive element is fluorine
11Periodic Table 101
- The PT is organized into vertical columns called
groups or families. - There are 18 columns
- Each family contains elements with similar
chemical characteristics - Each element in a family has the same number of
valence electrons - This makes it somewhat predictable as to how the
atom will behave in chemical reaction
12PNICOGENS
CHALCOGENS
13Periodic Table 101
- Elements in a group tend to form ions of the
same charge. - Modeled by electron configurations.
14Periodic Table 101
He
O
He
15The Transition Metals are almost unpredictable,
and sometimes have more than one possible charge
-- due to the d orbitals --
16Periodic Trend of Ionic Charges
17Tend to lose electrons to become positive
Tend to gain electrons to become negative
18Periodic Table 101
- The horizontal rows of elements in the PT are
called periods. - Physical and chem characteristics change
predictably across the period - Elements close to each other tend to have similar
characteristics, while elements farther apart
become increasingly different
19Periodic Table 101
- The two sets of elements below the PT make up
what are called the lanthanide and actinide
series. - They are metallic and radioactive and should be
placed after elements 57 89
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21Periodic Properties
- An elements properties can go hand in hand with
electron arrangement - We can use an elements location on the PT to
predict many properties. - Atomic radius
- Ionic Size
- Ionization energy
- Electron affinity
- Electronegativity
22Periodic Properties
- The radius of an atom is defined by the edge of
its last energy level. - However, this boundary is fuzzy
- An atoms radius is the measured distance between
the nuclei of 2 identical atoms chemically
bonded together - divided by 2.
23Periodic Properties
- As we examine atomic radius from left to right
across the PT we see a grad-ual decrease in
atomic size. - As e- are added to the s and p sublevels in the
same energy level, they are gradually pulled
closer to the highly positive nucleus - The more e-s in the atom the less dramatic this
trend looks
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25Periodic Properties
- The change in atomic radii across the PT is due
to e- shielding or to the effective nuclear
charge - As we move across the
PT we are adding e- into
the same gen- eral vol.
in which case they are
being shielded
or screened by interior
electrons, but the
shielding isnt
increasing
26Periodic Properties
- We are also adding protons into the nucleus which
increases the p-e- interaction (attraction) - So the nucleus gains strength while the e- arent
gaining much distance, so the atom is drawn in
closer and closer to the nucleus. - Decreasing the overall radius of
the atom
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30Periodic Properties
- How does the size of an atom change when
electrons are added or removed?
As an Atom loses 1 or more electrons (becomes
positive), it loses a layer therefore, its radius
decreases.
31Periodic Properties
- How does the size of an atom change when
electrons are added or removed?
As an Atom gains 1 or more electrons
(negative), it fills its valence layer,
therefore, its radius increases.
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33Periodic Properties
- Another periodic trend on the table is ionization
energy (a.k.a. potential) - Which is the energy needed to remove one of an
atoms e-s. - Or a measure of how strongly an atom holds onto
its outermost e-s. - If the e-s are held strongly the atom will have a
high ionization energy
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37Periodic Properties
- The ionization energy is generally measured for
one electron at a time - You can also measure the amount of energy needed
to reach in and pluck out additional electrons
from atoms. - There is generally a large jump in energy
necessary to remove additional electrons from the
atom.
38the amount of energy required to remove a 2p e
(an e- in a full sublevel) from a Na ion is
almost 10 times greater than that required to
remove the sole 3s e-
39Periodic Properties
- Another periodic trend dealing with an e- is
electron affinity - Which is a measure of the ability of an atom to
attract or gain an electron. - Atoms that tend to accept an e- are those that
tend to give a neg. charge. - The closer to a full outer shell an atom has, the
higher the affinity (more neg. the measurement)
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42Periodic Properties
- An atoms ability to lose an e- or gain an e- can
be used to understand the Octet Rule - Octet Rule atoms tend to gain, lose, or share
electrons in order to acquire a full set of
valence electrons. - 2 e- in the outermost s sublevel 6 e in the
outermost p sublevel a full valence shell
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45Periodic Properties
- Electronegativity is a key trend.
- It reflects the ability of an atom to attract
electrons in a chemical bond. - F is the most electronegative element and it
decreases moving away from F. - Electronegativity correlates to an atoms
ionization energy and electron affinity
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49BOILING POINT MELTING POINT VS. ATOMIC NUMBER
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53Electronegativity
Electronegativity
54Electronegativity
Electronegativity