Transcript Chapter 5 power point

Periodic Relationships
Among the Elements
Chapter 5
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
History of the Periodic Table
Dimitri Mendeleev
•Arranged the elements by increasing
ATOMIC MASS and saw a periodic repetition
of properties
•Produced the first PERIODIC TABLE – 1871
•The table placed elements with similar
properties in the same column
•Kept “holes” for undiscovered elements, and
predicted the properties in advance
Properties of elements predicted by Mendeleev
H.G. Moseley in 1914
• Rearranged the elements by:
ATOMIC NUMBER
• This has become the
MODERN PERIODIC TABLE
Electrons and Ions on the
Periodic Table
Review: Valence Electrons
What are valence electrons?
*Remember: Elements in a group have
similar properties because they have
the same valence electron configuration
Valence Electron Configuration
Group
e- config
1
ns1
2
ns2
13
ns2np1
14
ns2np2
15
ns2np3
16
ns2np4
17
ns2np5
18
ns2np6
Valence
electrons
Expected
Charges
-1
-2
-3
+3
+2
+1
Charges Of Representative Elements
8.2
Isoelectronic:
Elements and ions that have the
same number of electrons and
therefore the same electron
configuration
What ions are isoelectronic with Neon?
What would the electron configuration be?___________
Na+
F-
Mg2+
O2-
Al3+
N3-
Forming Ions with Transition Metals
When a cation is formed from an atom of a transition
metal, electrons are always removed first from the s
orbital and then from the d orbitals.
Fe:
[Ar]4s23d6
Fe2+: [Ar]4s03d6 or [Ar]3d6
Fe3+: [Ar]4s03d5 or [Ar]3d5
Mn:
[Ar]4s23d5
Mn2+: [Ar]4s03d5 or [Ar]3d5
Periodic Table Groups and
Properties
Periodic Table Groups
Properties of Metals
1.
2.
3.
4.
shiny (luster)
conductors of heat and electricity
reactive with acids
ductile
– can be stretched into a wire
5. malleable
– can be hammered or rolled into sheets
6.
forms positive ions (by losing e-)
Properties of Nonmetals
1. dull and brittle
2. poor conductors of heat and
electricity
3. does not react with acids
4. usually gases at room temp.
5. forms negative ions (by gaining e-)
What are properties of Metalloids??
•In the middle!
•Metalloids have properties of
BOTH!! (metals and nonmetals)
Periodic Trends
PERIODIC LAW
When elements are arranged in order of
increasing atomic number, their physical
and chemical properties show a periodic
(repeating) pattern.
patterns on the periodic table are called
periodic trends
Atomic Radius
half the distance from center-center of 2
like atoms
Atomic Radii DOWN a Group
↓As you go down there are more
energy levels, the atom size gets
larger
↓There are more electrons between
the nucleus and the outermost
energy level which increases the
shielding effect
Shielding Effect
• reduction of attraction between
positive nucleus and outermost
electrons
•outer electrons are not held tight and
can move away
Atomic Radius: down group
P
X
Na
X
P P
P
P P
P P
P
P P
P
X
X
X
X
X
X
X
X
X
X
Atomic Radius: down group
P
X
K
X
P P
P
P P
P P
P
P P
P
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Atomic Radii DOWN a Group
↓DOWN THE GROUP ATOMIC RADIUS
INCREASES
more energy levels,
the larger the size of the atom
Atomic Radii ACROSS a Period
→ Each atom gains one proton and
one electron in the same energy
level
→Each added electron is the same
distance from the nucleus
→The positive charge increases and
exerts a greater force on the
electrons pulling them closer to the
nucleus
REMEMBER!
PROTONS
are bigger
and stronger!
+
+
P
e
-electrons
are smaller
and weaker!
Atomic Radii ACROSS a Period
Effective nuclear charge:
“positive charge” felt by an electron.
Within a period, every time a proton is
added, the effective nuclear charge
increases… so the radius decreases
Ask yourself, how effective are the positive
protons pulling in the electrons?
Atomic Radius: across period
P
X
X
P P
P
P
P
P P
P P
P
X
X
X
X
X
X
X
X
X
Atomic Radii ACROSS a Period
→ACROSS THE PERIOD ATOMIC RADIUS
DECREASES
greater effective nuclear charge (more protons),
greater pull on the electrons, smaller radius
Ionic Radii
half the distance from centercenter of 2 like ions
Ionic Radius DOWN a Group
↓As you go down a group another
energy level is added, increasing the
size of the atom.
(just like the atomic radius)
Ionic Radius DOWN the Group
↓DOWN THE GROUP IONIC RADIUS
INCREASES
more energy levels,
increase in atom size
Ionic Radius ACROSS the Period
Cation: positive ion formed from
losing an electron
→ A cation is always smaller than
the original atom
→The more electrons lost the more
protons available to attract a
smaller number of electrons.
Ionic Radius
P
X
Na +
P P
P
P P
P P
P
P P
P
X
X
X
X
X
X
X
X
X
X
X
Ionic Radius ACROSS the Period
→ACROSS THE PERIOD IONIC RADIUS
DECREASES
greater effective nuclear charge, less
electrons, the shorter the radius
Ionic Radius ACROSS the Period
Anion: negative ion formed from
gaining an electron
→ A anion is always larger than the
original atom
→The more electrons gained, the
less protons available to attract a
larger number of electrons.
Ionic Radius
P
X
FP P
P
P P
P P
P
P P
P
X
X
X
X
X
X
X
X
X
X
Ionic Radius ACROSS the Period
→ACROSS THE PERIOD IONIC RADIUS
DECREASES
As electrons are added the atom gets
larger from right to left,
General trend from left to right is decreasing
Ionic Radii
Ionization Energy
amount of energy needed to
remove an electron from an atom
Multiple Ionization Energies
X
X+ + e-
I1 first ionization energy
X
X2++ e-
I2 second ionization energy
X
X3++ e-
I3 third ionization energy
I1 < I2 < I3
Ionization Energy DOWN a Group
↓As you go down a group atoms
become larger
↓The more electrons in an atom
between the nucleus and valence
shell, the greater the shielding
effect
Ionization Energy DOWN a Group
↓DOWN THE GROUP IONIZATION ENERGY
DECREASES
greater distance from the nucleus,
greater shielding effect
less energy needed to remove electron
Ionization Energy ACROSS a Period
→As atomic radius decreases there
is a greater attraction between
protons and electrons. (effective
nuclear charge)
→The stronger the attraction, the
more energy needed to remove an
electron.
Ionization Energy ACROSS a Period
→ACROSS THE PERIOD IONIZATION ENERGY
INCREASES
greater the effective nuclear charge,
more energy required to remove electron
Electronegativity
ability of an atom to attract electrons
It is a “tug of war” between the two
atoms of a bond .
:
.
H . F
:
:
Which is the more electronegative element?
Electronegativity
DOWN the Group
↓The farther away from the nucleus,
the greater the shielding effect
↓The larger the atom, the less likely it
is to accept more electrons.
Electronegativity
DOWN the Group
↓DOWN THE GROUP ELECTRONEGATIVITY
DECREASES
farther the distance from the nucleus,
lower ability to attract electrons
Electronegativity
ACROSS the Period
→As you go across a period atomic
radius decreases because there is a
greater effective nuclear charge
→Metals do not attract electrons.
→Non-metals do attract electrons.
Electronegativity
ACROSS the Period
→ACROSS THE PERIOD ELECTRONEGATIVITY
INCREASES
greater effective nuclear charge,
greater ability to attract electrons
Electron Affinity
the energy change that occurs when an
electron is added to an atom to form an
anion.
Increases with ability to attract and hold
an electron (electronegativity)
Electron Affinity
DOWN the Group
↓The larger the atom the more
difficult to accept electrons
Electron Affinity
DOWN the Group
↓DOWN THE GROUP ELECTRON AFFINITY
DECREASES
farther the distance from the nucleus,
does not want to gain electrons
Electron Affinity
ACROSS the Period
→As effective nuclear charge gets
stronger, it is easier to attract an
electron.
Electron Affinity
ACROSS the Period
→ACROSS THE PERIOD ELECTRON AFFINITY
INCREASES
greater effective nuclear charge,
easily forms anions
Other Trends
Reactivity of Metals Video 1
Reactivity of Metals Video 2
Increasing reactivity
METAL REACTIVITY
Increasing reactivity
NONMETAL REACTIVITY