The Periodic Table got its name because of the repeating pattern of chemical amp physical properties Mendeleev ordered his periodic table with elements arranged in order of increasing atomic ID: 933584
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Slide1
Chapter 6
Periodic Table and Periodic Law
Slide2The Periodic Table got its name because of the repeating pattern of chemical & physical
properties
.Mendeleev ordered his periodic table with elements arranged in order of increasing atomic mass.
Slide3Mendeleev noticed there seemed to be a
repeating
pattern of properties such as densities, formulas with oxygen & hydrogen, boiling or melting points every 8 or 18 elements. He called this repeating quality, periodic. (Periodic ~ according to a pattern)He
started new rows so that the elements having the same properties would be aligned in each column.
Holes for undiscovered elements
Similar properties in each column
Slide4He also noticed some gaps -
missing
elements Based on his periodic table Mendeleev predicted
the properties of the missing elements. Others tried to prove him wrong, but it turns out that he was right. Scientists soon found the missing elements and Mendeleev was
very close
with his predictions.
Slide5Mendeleev’s Predictions
Ekasilicon (Es)
Germanium (Ge)
Atomic mass
72
Density
5.5 g/cm
3
Melting point
High
Color
Dark gray metal
Obtained in
K
2
EsF
6
Will form
EsO
2
Density of oxide
4.7 g/cm
3
Solubility
Slightly in HCl
Slide6Mendeleev’s Predictions
Ekasilicon (Es)
Germanium (Ge)
Atomic mass
72
72.61
Density
5.5 g/cm
3
Melting point
High
Color
Dark gray metal
Obtained in
K
2
EsF
6
Will form
EsO
2
Density of oxide
4.7 g/cm
3
Solubility
Slightly in HCl
Slide7Mendeleev’s Predictions
Ekasilicon (Es)
Germanium (Ge)
Atomic mass
72
72.61
Density
5.5 g/cm
3
5.323 g/cm
3
Melting point
High
Color
Dark gray metal
Obtained in
K
2
EsF
6
Will form
EsO
2
Density of oxide
4.7 g/cm
3
Solubility
Slightly in HCl
Slide8Mendeleev’s Predictions
Ekasilicon (Es)
Germanium (Ge)
Atomic mass
72
72.61
Density
5.5 g/cm
3
5.323 g/cm
3
Melting point
High
945
o
C
Color
Dark gray metal
Obtained in
K
2
EsF
6
Will form
EsO
2
Density of oxide
4.7 g/cm
3
Solubility
Slightly in HCl
Slide9Mendeleev’s Predictions
Ekasilicon (Es)
Germanium (Ge)
Atomic mass
72
72.61
Density
5.5 g/cm
3
5.323 g/cm
3
Melting point
High
945
o
C
Color
Dark gray metal
Gray metal
Obtained in
K
2
EsF
6
Will form
EsO
2
Density of oxide
4.7 g/cm
3
Solubility
Slightly in HCl
Slide10Mendeleev’s Predictions
Ekasilicon (Es)
Germanium (Ge)
Atomic mass
72
72.61
Density
5.5 g/cm
3
5.323 g/cm
3
Melting point
High
945
o
C
Color
Dark gray metal
Gray metal
Obtained in
K
2
EsF
6
K
2
GeF
6
Will form
EsO
2
Density of oxide
4.7 g/cm
3
Solubility
Slightly in HCl
Slide11Mendeleev’s Predictions
Ekasilicon (Es)
Germanium (Ge)
Atomic mass
72
72.61
Density
5.5 g/cm
3
5.323 g/cm
3
Melting point
High
945
o
C
Color
Dark gray metal
Gray metal
Obtained in
K
2
EsF
6
K
2
GeF
6
Will form
EsO
2
Forms GeO
2
Density of oxide
4.7 g/cm
3
Solubility
Slightly in HCl
Slide12Mendeleev’s Predictions
Ekasilicon (Es)
Germanium (Ge)
Atomic mass
72
72.61
Density
5.5 g/cm
3
5.323 g/cm
3
Melting point
High
945
o
C
Color
Dark gray metal
Gray metal
Obtained in
K
2
EsF
6
K
2
GeF
6
Will form
EsO
2
Forms GeO
2
Density of oxide
4.7 g/cm
3
4.70 g/cm
3
Solubility
Slightly in HCl
Slide13Mendeleev’s Predictions
Ekasilicon (Es)
Germanium (Ge)
Atomic mass
72
72.61
Density
5.5 g/cm
3
5.323 g/cm
3
Melting point
High
945
o
C
Color
Dark gray metal
Gray metal
Obtained in
K
2
EsF
6
K
2
GeF
6
Will form
EsO2Forms GeO2Density of oxide4.7 g/cm34.70 g/cm3Solubility Slightly in HClNot dissolved in HCl
https://www.youtube.com/watch?v=kuQ0Um4Wcz0
Slide14In the modern Periodic Table, elements are arranged in order of increasing atomic
number
.
Slide15The
horizontal rows are called
periods. The vertical columns are called
groups.
The patterns of properties repeat in each new row, so elements in the
columns
, have similar chemical and physical properties. This is called the periodic
Law
Slide16The group A elements (the
s&p
blocks) are called the representative elements. 1A 2A 3A 4A 5A 6A 7A 8A
Slide17The
group B elements (the d block) are called the
transition elements.The group B elements (the f block) are called the inner
transition elements.
Transition
Inner
Transition
Slide18There are 3 main classes of elements:
metals,
nonmetals,
metalloids.
Slide19The electron structure of an atom determines many of its
chemical & physical
properties. For the group A elements, the group number equals the number of valence electrons. (Except for Helium=2)
Slide20The Octet rule states that atoms lose, gain, or
share
electrons in order to gain a full set of 8 valence electrons. This noble gas configuration is very stable. (the exceptions are Hydrogen and helium which will have a stable set of 2 electrons in the 1
st energy level). Using the octet rule, you can predict which ions will likely form.
Neon has full outer
shell : stable &
nonreactive
Slide21Metals are electron
donors
. They tend to lose electrons and become + (positive) charged ions.
Called a cation.
Na has 1 valence electron
Must lose 1 electron to have full outer shell
(easier to lose 1 than gain 7)
Creates a ion with a +1 charge
Slide22Nonmetals
are electron
acceptor. They tend to gain electrons and become – (negative) charged ions.
Called an anion.
Chlorine has 7 valence electrons
Need 1 more electron to gain full outer shell
Creates -1 ion
Slide23Periodic trends
Atomic radius
: Tends to decrease across the period. Electrons are being added in the same energy level so increased attraction between the larger number of + protons pulls the – electrons closer.
Slide24Periodic trends
Atomic radius
: Tends to increase down the group, because you are adding energy levels, which
shield the valence electrons from the pull of the nucleus.
Slide25Ionic radius
Losing electrons produce
+ charged ions, which are smaller than the parent atom.
Slide26Cation Formation
11p+
Na atom
1 valence electron
Valence e- lost in ion formation
Effective nuclear charge on remaining electrons increases.
Remaining e- are pulled in closer to the nucleus. Ionic size decreases.
Result: a smaller sodium cation, Na
+
Slide27Ionic radius
When
atoms gain electrons, they become –
charged ions, which are larger than the parent atom.
Slide28Anion Formation
17p+
Chlorine atom with 7 valence e-
One e- is added to the outer shell.
Effective nuclear charge is reduced and the e- cloud expands.
A chloride ion is produced. It is larger than the original atom.
Slide29Ionic radius
As
with the atomic radius size, decrease across the periods an
increase down the group. Notice difference between cations & anions; but trends are still same
decreases
increases
Slide30Ionic Radius
– size as compared to the
neutral element
- Positive cations are always smaller than neutral atom (removal of e-
) often remaining e
-
are in a lower energy level.Na 1s
22s22p
63s1 Na1+
1s
2
2
s
2
2p
6
-
Anions
get bigger than neutral atom. Adding e
-
creates more e
-
repulsion.
Cl
1s
2
2
s22p63s23p5 Cl1- 1s22s22p63s23p6
Slide31Ionization energy
Is the amount of energy required to pull the 1
st valence electron away from the atom.
Elements with high ionization energy are [unlikely, likely] to lose electrons. Atoms with low ionization energy [easily, don’t really] lose electrons
Slide32Ionization energy
Generally
metals have low ionization energies and easily form positive ions… nonmetals have high ionization energies and tend to form – ions.
Mostly +2 & +3
Noble gases:
do not form ions
Slide33Ionization energy
Ionization
energies increase across the period, because the atoms are getting smaller and the electrons closer to the nucleus
and harder to pull away.
Increases
Slide34Ionization energy
Ionization energies decrease moving down the group because the size of the atom is
larger so the electrons are farther away and easier to remove.
In other words the outer
e
lectrons are
shielded
from the pull of the nucleus by the inner shells
decreases
Slide35Electron Affinity
E.A. the amount of energy released when an atom gains an e
-.The opposite process of ionization. (removing of e
-) “affinity” means fondness.~ E.A.
increases
across a period.
Why? Nonmetals give off more energy when they gain an e
- than metals do.~ E.A. decreases
down a family. Why? b/c of the larger # of e- less energy is given off w/the addition of one more e-.
Slide36Electronegativity
Indicates the elements relative ability to gain electrons in a chemical bond. The greater the
electronegativity the greater the attraction for electrons. How strongly the element “wants” the electron, so metals are low; nonmetals are high
Slide37Electronegativity
Fluorine
is the most electronegative element and Francium is the least. Increases across the periods and
decreases down the group.
0
Fr
F
decreases
increases
Slide38Two most important trends are atomic radius and
electronegativity
.*For all trends except size & #, the closer you are to F, the greater the trend
Slide39In summary:
*Atomic number:
a period a family
*Atomic radius: a period a family*Ionic radius:
Positive
cations
vs. neutral atom
Negative anions vs. neutral atom
Slide40*Ionization Energy:
a period a family
*Electron Affinity: a period a family
*Electronegativity:
a period a family
Slide41Some specific groups:
Group IA
Alkali metals: Li, Na, K,
Rb, Cs, FrIn pure state have a silvery appearance and are soft enough to cut with a knife. Yet, alkali metals are so reactive they are not found in nature as free elements. Combine vigorously w/most nonmetals. Usually stored in Kerosene.
Slide42Group IIA
Alkaline earth metals
: Be, Mg, Ca, Sr, Ba, Ra
Have 2e- in outermost level. They are harder, denser, and stronger than alkali metals. Although they are less reactive than group IA, they are too reactive to be found alone in nature.
Slide43Group VII A
Halogens
: F, Cl, Br, I, AtMost reactive nonmetals. React vigorously w/most metals to form a type of compound known as salts. Has 7e
- in its outer energy level.
Slide44Group VIII A
Noble Gases
: He, Ne, Ar, Kr, Xe,
RnThese are the least reactive of all the elements. Have very stable electron configurations. For many years, the noble gases were believed to be chemically unreactive
, yet in the lab inert gas compounds can be synthesized.
Slide45On the Periodic table above label:
1) Alkali Metals, 2) Alkaline Earth Metals,
3) Halogens, 4) Noble Gases, 5) Metals,
6) Nonmetals, 7) Metalloids, 8) Transition Metals,9) Inner Transition Metals
Slide46Noble
Gas
Metalloids
(on the stair-step line)
Inner Transition Metals
(f – block elements)
Slide472. Explain why the word
periodic
is applied to the table of elements.The pattern of properties repeats periodically with each new row
Slide483. Why do elements in a
group
(vertical column) in the periodic table exhibit similar chemical properties? They have the same arrangement of valence electrons
Slide494. What chemical property is common to the elements in group 8A. Explain why.
Group 8A = noble gases = chemically
unreactive
because they have a full set of 8 (octet) valence electrons
Slide505. In terms of electron configuration, what does the group number of the A-groups tell you?
The A-group number = the number of valence electrons
Slide516. Describe the relationship between the
electronegativity
value of an element and the tendency of that element to gain or lose electrons when forming a chemical bond.The higher the
electronegativiy, the greater the tendency to gain an electron.
Slide52Decrease
Increase
7. Describe the group and period trends in the following atomic properties
Atomic Radius &
Ionic Radius
Slide53Increase
Decrease
7. Describe the group and period trends in the following atomic properties
Electronegativity
&
First Ionization Energy