Transcript Chapter 6.3 Periodic Trends

6.3
Periodic Trends
Sodium chloride (table salt)
produced the geometric
pattern in the photograph.
Such a pattern can be used
to calculate the position of
nuclei in a solid. You will
learn how properties such
as atomic size are related to
the location of elements in
the periodic table.
Chapter 6 The Periodic Table
6.3 Periodic Trends
Today we are learning to:1. Describe trends in the periodic table for atomic size
2. Explain how ions form
3. Describe periodic trends for 1st ionization energy, ionic size and
electronegativity
6.3
Trends in Atomic Size
The atomic radius is one half of the distance between the
nuclei of two atoms of the same element when the atoms are
joined.
Trends in Atomic Size
The are 3 main factors that will have an effect on the size on an atom.
1. Nuclear charge (the charge on the nucleus). A larger positive charge on a
nucleus will pull electrons closer to it.
2. The number of the outermost energy level containing electrons. n = 3 is
further from the nucleus than n = 2.
3. The number of inner electrons shielding the outer electrons from the nucleus
Periodic Trends Atomic Radius
Trends in Atomic Size
Group and Periodic Trends in Atomic Size
In general, atomic size increases from top to bottom within a group and
decreases from left to right across a period.
Radius (pm)
250
K
1st transition
series
3rd period
200
Na
2nd period
Li
150
Kr
100
Ar
Ne
50
He
0
0
5
10
15
20
Atomic Number
25
30
35
40
6.3
Trends in Atomic Size
Size goes UP on going down a group.
Because electrons are added farther from the nucleus, there is less
attraction.
Size goes DOWN on going across a period.
Because of greater nuclear attraction
Atomic Radii
6.3
Trends in Ionic Size
Positive and negative ions form when
electrons are transferred between atoms.
6.3
Trends in Ionic Size
Positive and negative ions form when
electrons are transferred between atoms.
6.3
Trends in Ionic Size
Ions
Some compounds are composed of particles called ions.
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•
•
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An ion is an atom or group of atoms that has a positive or negative charge.
A cation is an ion with a positive charge.
An anion is an ion with a negative charge.
Metal atoms tend to lose electrons, and nonmetal atoms tend to gain
electrons when they react together. The transfer of electrons effects the size
of the ions formed
•
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Cations are always smaller than the atoms from which they form.
Anions are always larger than the atoms from which they form.
Trends in Ionic Size
Li,152 pm
3e and 3p
Does+the size go
up+or down when
Li , 60 pm
losing
2e and 3an
p electron
to form a cation?
Trends in Ionic Size
+
Li,152 pm
3e and 3p
Li + , 78 pm
2e and 3 p
Forming a
cation.
CATIONS are SMALLER than the
atoms from which they come.
There is no longer an electron in
the 2s orbital and so size
DECREASES.
Does the size go up or
down when gaining an
electron to form an
anion?
Trends in Ionic Size
F, 71 pm
9e and 9p
F- , 133 pm
10 e and 9 p
Forming
an anion.
ANIONS are LARGER than the atoms
from which they come.
The electron/electron repulsion in the
2p orbital increases because of the
extra electron and so size INCREASES.
Trends in ion sizes are the same as
atom sizes.
6.3
Trends in Ionic Size
Relative Sizes of Some Atoms and Ions
Trends in Ionic Size
6.3
Trends in Ionic Size
Size generally increases
Trends in Ionic Size
Trends in Ionic Size
6.3
6.3
Trends in Ionization Energy
The energy required to remove an electron from an atom in its gaseous state is
called ionization energy. Unit of measurement is KJ/mol (kilojoules per mole)
•
The energy required to remove the first electron from an atom is called the
first ionization energy.
•
The energy required to remove an electron from an ion with a 1+ charge is
called the second ionization energy.
•
First ionization energy tends to decrease from top to bottom within a
group and increase from left to right across a period.
6.3
Trends in Ionization Energy
6.3
Trends in Ionization Energy
6.3
Trends in Ionization Energy
6.3
Trends in Electronegativity
Electronegativity is the ability of an atom of an element to attract electrons
when the atom is in a compound.
In general, electronegativity values decrease from top to bottom within a group.
For representative elements, the values tend to increase from left to right across
a period.
6.3
Trends in Electronegativity
Representative Elements in Groups 1A through 7A
6.3
Summary of Trends
Increases Decreases
Size
Electronegativity
Ionic
Atomic
Nuclear
Shielding
Ionization
of
size
cations
Size
anions
Charge
energy
Increases
Decreases
Constant
Summary of Trends
The succession of elements within a group demonstrates characteristic
trends in properties. As you progress down a group:
1.
atomic radius increases.
2.
electronegativity decreases.
3.
first ionization energy decreases.
4.
Ionic size increases.
Section Assessment
Summary of Trends
The succession of elements within a period demonstrates characteristic
trends in properties. As you progress across a group from left to right:
1.
atomic radius decreases.
2.
electronegativity increases.
3.
first ionization energy increases.
4.
Ionic size decreases.
6.3 Section Quiz
1. Which of the following sequences is correct
for atomic size?
a. Mg > Al > S
b. Li > Na > K
c. F > N > B
d. F > Cl > Br
6.3 Section Quiz
2. Metals tend to
a. gain electrons to form cations.
b. gain electrons to form anions.
c. lose electrons to form anions.
d. lose electrons to form cations.
6.3 Section Quiz
3. Which of the following is the most
electronegative?
a. Cl
b. Se
c. Na
d. I
6.3 Section Quiz
4. How does the size of a barium ion compare with
the size of a barium atom?
a. The ion is smaller because it has fewer
electrons
b. The ion is smaller because it has more
electrons
c. The ion is larger because it has fewer electrons
d. The ion is larger because it has more electrons
6.3 Section Quiz
5. Which ion has the largest radius?
a. Na+
b. Mg 2+
c. K +
d. Ca 2+
6.3 Section Quiz
6. Which of the following is the most
electronegative?
a. Cl
b. Se
c. Na
d. I
6.3 Section Quiz
7. Which element has the highest first
ionization energy?
a. sodium
b. aluminum
c. calcium
d. phosphorus
6.3 Section Quiz
9. Properties of metals include
a. Low ionization energy and high
electronegativity
b. Low ionization energy and low
electronegativity
c. High ionization energy and high
electronegativity
d. High ionization energy and low
electronegativity
6.3 Section Quiz
10. An element has a 1st ionization energy of
1314KJ/mol and an electronegativity of 3.5.
It is classified as a
a. metal
b. nonmetal
c. metaloid
d. halogen
6.3 Section Quiz
1. Which of the following sequences is correct
for atomic size?
a. Mg > Al > S
b. Li > Na > K
c. F > N > B
d. F > Cl > Br
6.3 Section Quiz
2. Metals tend to
a. gain electrons to form cations.
b. gain electrons to form anions.
c. lose electrons to form anions.
d. lose electrons to form cations.
6.3 Section Quiz
3. Which of the following is the most
electronegative?
a. Cl
b. Se
c. Na
d. I
6.3 Section Quiz
4. How does the size of a barium ion compare with the
size of a barium atom?
a. The ion is smaller because it has fewer electrons
b. The ion is smaller because it has more electrons
c. The ion is larger because it has fewer electrons
d. The ion is larger because it has more electrons
6.3 Section Quiz
5. Which ion has the largest radius?
a. Na+
b. Mg 2+
c. K +
d. Ca 2+
6.3 Section Quiz
6. Which of the following is the most
electronegative?
a. Cl
b. Se
c. Na
d. I
6.3 Section Quiz
7. Which element has the highest first
ionization energy?
a. sodium
b. aluminum
c. calcium
d. phosphorus
6.3 Section Quiz
9. Properties of metals include
a. Low ionization energy and high
electronegativity
b. Low ionization energy and low
electronegativity
c. High ionization energy and high
electronegativity
d. High ionization energy and low
electronegativity
6.3 Section Quiz
10. An element has a 1st ionization energy of
1314KJ/mol and an electronegativity of 3.5.
It is classified as a
a. metal
b. nonmetal
c. metaloid
d. halogen
END OF SHOW