THE PERIODIC TABLE
1869 DMITRI MENDELEEV
Arranged the elements by increasing atomic mass, and
noticed properties repeat regularly
Left a space if an element didn’t belong in a particular column
1H-1 (of 10)
Mendeleev stated the PERIODIC LAW:
The properties of the chemical elements are not arbitrary, but
vary with their atomic masses in a systematic way
Mendeleev was able to predict properties of undiscovered
elements
However, accurate atomic mass determinations showed errors in the table
1H-2 (of 10)
1912 HENRY MOSELEY
Measured the frequency of x-rays from excited atoms
Found they were proportional to the ATOMIC NUMBER of the
atoms, not the atomic mass
1H-3 (of 10)
1912 HENRY MOSELEY
This work changed the PERIODIC LAW:
The properties of the chemical elements vary with atomic
number
1H-4 (of 10)
PERIOD or SERIES – A row
GROUP or FAMILY – A column
Elements in columns have similar properties because they have the same
number of valence electrons
1H-5 (of 10)
PERIODIC TRENDS OF ATOMS
The attraction of either (1) outer shell electrons or (2) free electrons to the
nucleus of an atom depends on
(1) The number of protons in nucleus
(2) The number of energy levels blocking or SHIELDING the nucleus from
the outer shell or free electrons
1H-6 (of 10)
1)
ATOMIC RADIUS – The distance from the nucleus to the outer shell of
an atom
1H-7 (of 10)
PERIODIC TRENDS IN ATOMIC RADII
Period – The atomic radii decrease moving to the right
the outer shell electrons are attracted by an increasing nuclear charge,
while the shielding of the nuclear charge remains the same
Group – The atomic radii increase moving down a column
even though the nuclear charge is increasing,
the outer shell electrons are more shielded from the nuclear charge
Atom with the largest atomic radius ?
Atom with the smallest atomic radius?
1H-8 (of 10)
1H-9 (of 10)
EXCEPTIONS TO THE TRENDS IN ATOMIC RADII
Group
Atoms in the 5d sublevel section of the periodic table are not larger than
atoms in the 4d sublevel section
Radii
V
Increasing
Factor
Decreasing
Factor
(Z = 23)
0.122 nm
Nb (Z = 41)
0.134 nm
1 more EL
18 more p+
Ta (Z = 73)
0.134 nm
1 more EL
32 more p+
This is called the LANTHANIDE CONTRACTION
1I-10 (of 10)
2)
IONIZATION ENERGY (IE) – The energy change for the removal of an
electron from a gaseous atom
X (g) → X+ (g) + eEndothermic – A process in which energy is absorbed
(∆E is positive)
Exothermic
– A process in which energy is released
(∆E is negative)
Ionization Energies are always endothermic
1I-1 (of 15)
SUCCESSIVE IONIZATION ENERGIES
→ Mg+ (g) + e-
1st IE =
736 kJ/mol
Mg+ (g) → Mg2+ (g) + e-
2nd IE =
1,451 kJ/mol
Mg2+ (g) → Mg3+ (g) + e-
3rd IE =
7,728 kJ/mol
Mg3+ (g) → Mg4+ (g) + e-
4th IE = 10,534 kJ/mol
Mg (g)
Successive ionization energies always increase because successive ions
have less e--e- repulsion
1I-2 (of 15)
SUCCESSIVE IONIZATION ENERGIES
→ Mg+ (g) + e-
1st IE =
736 kJ/mol
Mg+ (g) → Mg2+ (g) + e-
2nd IE =
1,451 kJ/mol
Mg2+ (g) → Mg3+ (g) + e-
3rd IE =
7,728 kJ/mol
Mg3+ (g) → Mg4+ (g) + e-
4th IE = 10,534 kJ/mol
Mg (g)
Successive ionization energies always increase because successive ions
have less e--e- repulsion
Small ionization energies occur when removed e-s are valence e-s, which
are the most shielded from the nuclear charge
1I-3 (of 15)
Atom 1
Atom 2
1st IE =
496 kJ/mol
1st IE =
578 kJ/mol
2nd IE =
4,562 kJ/mol
2nd IE =
1,817 kJ/mol
3rd IE =
6,912 kJ/mol
3rd IE =
2,745 kJ/mol
4th IE =
9,543 kJ/mol
4th IE = 11,577 kJ/mol
Determine which atom is sodium and which atom is aluminum
Na
1I-4 (of 15)
Al
PERIODIC TRENDS IN 1st IONIZATION ENERGIES
Period – The 1st IE increases moving to the right
the removed electron is attracted by an increasing nuclear charge,
while the shielding of the nuclear charge remains the same
Group – The 1st IE decreases moving down a column
even though the nuclear charge is increasing,
the removed electron is more shielded from the nuclear charge
Atom with the highest 1st IE ?
1I-5 (of 15)
Atom with the lowest 1st IE?
1I-6 (of 15)
EXCEPTIONS TO THE TRENDS IN 1st IONIZATION ENERGIES
Period
Li
Be
519
900
1s
B
↑↓
___
B
C
N
O
F
Ne
799
1088
1406
1314
1682
2080
2s
↑↓
___
2p
↑___
___ ___
The removed e- for B is in a p orbital, whereas the removed e- for Be is in
an s orbital - e-s in p orbitals are more shielded from the nuclear charge
than e-s in s orbitals
1I-7 (of 15)
EXCEPTIONS TO THE TRENDS IN 1st IONIZATION ENERGIES
Period
Li
Be
519
900
1s
O
↑↓
___
B
C
N
O
F
Ne
799
1088
1406
1314
1682
2080
2s
2p
↑↓
↑↓
↑ ↑
___ ___ ___
___
The removed e- for O is paired and experiencing e--e- repulsion, whereas
the removed e- for N is not
1I-8 (of 15)
3)
ELECTRON AFFINITY (EA) – The energy change for the addition of an
electron to a gaseous atom
X (g) + e- → X- (g)
Electron Affinities are always exothermic
1I-9 (of 15)
PERIODIC TRENDS IN ELECTRON AFFINITIES
Period – EA increases (becomes more exothermic) moving to the right
a free electron is attracted by an increasing nuclear charge,
while the shielding of the nuclear charge remains the same
(except noble gases)
Group – EA decreases (becomes less exothermic) moving down a column
even though the nuclear charge is increasing,
a free electron is more shielded from the nuclear charge
1I-10 (of 15)
1I-11 (of 15)
EXCEPTIONS TO THE TRENDS IN 1st ELECTRON AFFINITIES
Group
In the p block of the periodic table, adding e-s to small atoms (those in the
2nd period) results in large e--e- repulsion, so their 1st EA’s are slightly less
exothermic than atoms in the 3rd period
F
-328 kJ/mol
Cl
-349 kJ/mol
Br
-343 kJ/mol
I
-295 kJ/mol
1I-12 (of 15)
← element with the highest EA
EXCEPTIONS TO THE TRENDS IN 1st ELECTRON AFFINITIES
Period
K
Ca
Ga
Ge
As
Se
Br
Kr
-49
~0
-76
-116
-75
-195
-325
~0
4s
↑↓
3d
4p
Ca
[Ar]
___
___ ___ ___ ___ ___
___ ___ ___
Kr
[Ar]
___
↑↓
↑↓
↑↓ ↑↓ ↑↓ ↑↓
___ ___ ___ ___ ___
___ ___ ___
↑↓ ↑↓ ↑↓
The added e- will go into an orbital of a new sublevel, where it will be
very shielded from the nuclear charge
1I-13 (of 15)
EXCEPTIONS TO THE TRENDS IN 1st ELECTRON AFFINITIES
Period
As
K
Ca
Ga
Ge
As
Se
Br
Kr
-49
~0
-76
-116
-75
-195
-325
~0
[Ar]
4s
3d
4p
↑↓
↑↓
↑↓ ↑↓ ↑↓ ↑↓
___ ___ ___ ___ ___
___ ___ ___
___
↑
The added e- will experience e--e- repulsion
1I-14 (of 15)
↑
↑
EXCEPTIONS TO THE TRENDS IN 1st ELECTRON AFFINITIES
Period
K
Ca
Ga
Ge
As
Se
Br
Kr
-49
~0
-76
-116
-75
-195
-325
~0
What other two elements in the 4th period would you expect to have
low electron affinities?
1I-15 (of 15)
Bismuth (Z = 83) – The element of highest atomic number with at least one
stable isotope
Plutonium (Z = 94) – The element of highest atomic number found naturally
on Earth
1J-13 (of 13)
METALS
Physical Properties – Low number of valence electrons, metallic luster,
malleable, ductile, conductors of heat and electricity
Solids are brilliant white (or silver) except copper (red) and gold (yellow),
mercury is a liquid
Chemical Properties – Due to the low ionization energies of their valence
electrons, they can lose their valence electrons to produce positive ions
(called CATIONS)
1J-1 (of 13)
Group 1
Group 2
- Alkali Metals
- Alkaline Earth Metals
Group 11
8, 9, 10
8, 9, 10
d Block
-
f Block
- Inner Transition Metals (Lanthanides and Actinides)
1J-2 (of 13)
Coinage Metals
Fe-Co-Ni Triad - The Ferromagnetic Metals
Noble Metals (Ru, Rh, Pd, Os, Ir, Pt)
Transition Metals
Metal Hardness
Group 1 metals are soft, hardness increases to Group 6, and then hardness
decreases to Group 16
1J-3 (of 13)
Metal Activity
Group 1 metals are extremely active, and activity decreases to Group 11,
with the Noble Metals, Coinage Metals, and Hg being very inactive
Al and Zn are very active, and activity decreases down and to the right
1J-4 (of 13)
NONMETALS
Physical Properties – High number of valence electrons, opposite of metals
Some are crystalline solids, bromine is a liquid, and some are gases
Chemical Properties – Due to their highly exothermic electron affinities, they
can gain electrons until their outer shells are full to produce negative ions
(called ANIONS)
1J-5 (of 13)
Group 18
Group 17
- Noble Gases
- Halogens
Hydrogen
- A group of its own in that it can form 1+ and 1- ions
1J-6 (of 13)
Hydrogen
-
Colorless gas (H2)
Helium
-
Colorless gas (He)
1J-7 (of 13)
Boron
- Crystalline brown
Carbon
- Crystalline as diamond,
graphite, or buckminsterfullerene; amorphous as
charcoal
ALLOTROPES – Forms of an element with
different interatomic bonding, so different
properties
1J-8 (of 13)
Nitrogen
- Colorless gas (N2)
Oxygen
- Colorless gas allotropes
dioxygen (O2) and ozone (O3)
Phosphorus
- Crystalline red, white (P4), and
black allotropes
Sulfur
- Crystalline yellow (S8 rings)
and other allotropes (S8
chains)
1J-9 (of 13)
Fluorine
- Pale yellow-green gas (F2)
Chlorine
- Yellow-green gas (Cl2)
Bromine
- Orange liquid (Br2)
Iodine
- Crystalline black (I2), sublimes
to violet vapor
Noble Gases
- Colorless monatomic gases
1J-10 (of 13)
Nonmetal Activity
Group 17 nonmetals are extremely active, and activity decreases down and
to the left
H is active, and the Noble Gases are inert
1J-11 (of 13)
METALLOIDS
Intermediate number of valence electrons, properties of metals and
nonmetals
1J-12 (of 13)