The Modern Periodic Table
Trends
Agenda
• Lesson: PPT,
• Handouts: 1.PPT Handout; Periodic Table
Puzzle; Periodic Table Worksheet
• Text: 1. P. 30-33; Organization of the periodic
table
• HW: 1. P. 33 # 1-4, 6; Finish all the
worksheets
The Modern Periodic Table
1. An arrangement of the elements in order of their
atomic numbers so that elements with similar properties
fall in the same column (or group).
• Groups: vertical columns (#1-18)
• Periodic: horizontal rows (# 1-7)
2. Periodicity – the similarities of the elements in the
same group is explained by the arrangement of the
electrons around the nucleus.
The s-block Elements: Groups 1
1
ns
1. Group 1: Alkali metals
• soft silvery metals
• most reactive of all metals, never found free in nature
• reacts with water to form alkaline or basic solutions
store under kerosene
• whenever you mix Li, Na, K, Rb, Cs, or Fr with water it
will explode and produce an alkaline solution
• ns1 (ending of all electron configurations for this
group)
The s-block Elements: Group
Alkaline earth metals- ns2
• less reactive than Alkali, but still react in water to
produce an alkaline solution
• never found free in nature
• harder, denser, stronger than alkali
• ns2 (ending of all electron configurations for this
group), because they have 2 electrons in the s sublevel,
this makes them a little less reactive then the Alkali
metals in group 1.
The d-Block Elements: Groups 3-12
• are all metals with metallic properties (malleability,
luster, good conductors, etc…); are referred to as the
Transition Metals
• Harder and denser than alkali or alkaline
• Less reactive than alkali or alkaline
• For the most part their outermost electrons are in a
d sublevel
• Exceptions to the electron configuration are found in
these groups (Ex: Ni, Pd, Pt)
The p – Block Elements: Groups 13 –
18 -np
• Contain metals and nonmetals
• Metalloids, along zigzag line, have characteristics of
both metals and nonmetals (many are good conductors
but are brittle). The metalloids are boron, silicon,
germanium, arsenic, antimony, and tellurium.
Group 17 - Halogens – most reactive
nonmetals-np5
• 7 electrons in outermost (s and p) energy levels (that
is why so reactive – only need one electron to have 8)
• called the salt formers (they react vigorously with
metals to form salts). A salt is a metal and a nonmetal
bonded together.
• most are gases
Group 18 - Noble gases –unreactive-np6
• 8 electrons in outermost s and p energy levels
• all are gases
• The s and p blocks are called the main group or
representative elements!
The f-Block Elements: Inner Transition
Metals
• final electrons fill an f sublevel
• Lanthanides – shiny reactive metals; Ce-Lu (fill the 4f
sublevel)
• Actinides – unstable and radioactive; Th-Lr (fill the 5f
sublevel)
Hydrogen and Helium - Oddballs
• Hydrogen is NOT an Alkali metal, it is a very reactive
gas. It is placed with the Alkali metals because 1s1 is
its electron configuration.
• Helium is a Noble gas, it is unreactive, but it does not
have 8 electrons in outermost energy level, because
it only has 2 total electrons!
# of Valence
Electrons
1
2
3
4
5
6
7
8
Group #
1
2
13
14
15
16
17
18
Ending Configuration
ns1
very reactive
ns2
np1
np2
np3
np4
np5
very reactive
np6
very unreactive
Agenda
Trends- Definitions
• Lesson: PPT
• Handouts: 1. Propeties of Atoms,
• Text: 1. P. 36-41-Trends parameters and
definitions
• HW: 1. Finish all the worksheets
Graphing Assignment
ATOMIC RADIUS
• Atomic radius is the distance from the centre of the
nucleus of an atom to the outermost electron.
• The greater the number of energy levels the greater
is the distance of the outermost electron to the
center of its atom’s nucleus.
• Ionic radius is the distance from the centre of the
nucleus of an ion to the outermost electron.
Cations will have a smaller ionic radius than the neutral
atom.
Anions will have a larger ionic radius than the neutral
atom.
FORCE OF ATTRACTION
• The force of attraction between negatively charged
electrons and the positively charged nucleus is the
electrostatic attraction of opposite charges.
• The force of attraction existing between the
outermost electron and the middle of the nucleus is
dependent on two factors:
1. The size of the positive charge - determined by the
number of protons in the nucleus.
2. The distance between the outermost electron and the
nucleus.
• A balance exists between the attraction of the
electrons to the nucleus and the repulsion of the
electrons between themselves
Trend in Atomic Radii
Group trend - atomic radii decrease as you move up a
group.
Period trend – atomic radii decrease as you move
across a period.
The size of an atomic
radius cannot be
measured exactly because
it does not have a sharply
defined boundary.
However the atomic radius
can be thought of as ½ the
distance between the
nuclei of identical atoms
joined in a molecule.
Atomic Radii Trend
Example: Which is larger? P atom or Cl atom
Example: Which would be larger? K+1 or K
Example: Which would be larger? K+1 or Ge+4
Graphing Assignment
Ionization Energy (IE)
• Ionization Energy is the energy in kilojoules per mole
(kJ/mol) needed to remove the outermost electron
from a gaseous atom to form a positive ion (cation)
Na + Energy  Na+ + e• neutral sodium has 11 protons and 11 electrons
• removal of 1 electron leaves 10 electrons and 11
protons and a net imbalance of charge of +1
NOTE: Metals react to lose electrons
The stronger an electron is held the greater the IE
needed to ionize (pull away) that electron
Successive Ionization Energy
• After the outermost electron (First IE) is removed the
successive ionization energies (Second and Third IE
and so on) increase as it becomes more difficult to
remove the next electrons since the pull of the
nucleus becomes stronger and electrons are more
tightly held.
Trend: Ionization Energy (IE)
Group trend – ionization energy increases as you move
up a group (or decreases as you move down a group).
Period trend – ionization energy increases as you move
across the period.
Which atom has the higher first
ionization energy?
(A) Hf or Pt
Pt
(B) Cl or Ar
Ar
Highest
IE Trend
ELECTRON AFFINITY [EA]
• Electron affinity is the energy released in kilojoules
per mole (kJ/mol) when an electron is captured by
an atom to form a negative ion (anion)
Cl + Electron  Cl- + Energy
• neutral chlorine has 17 protons and 17 electrons
• addition of 1 electron gives 18 electrons and 17
protons and a net imbalance of charge of -1
• NOTE: Nonmetals react to gain electrons
Trend: Electron Affinity (EA)
Period trend – electron affinity increases as you move
across a period because atoms become smaller and the
nuclear charge increases. This means there is a greater
pull from the nucleus.
Group trend – electron affinity increases as you move
up a group (or decreases as you move down a group)
because the size of the atom increases.
Highest
Example: Which element has
the greater electron affinity?
Pb or Sn
Sn
EA Trend
Electron affinity vs. Ionization energy
Electron affinity and Ionization energy follow the same
trend in the periodic table.
• The stronger the attraction an atom has for
electrons the harder it will be to remove electrons
from that atom and the higher the IE energy will be.
• The greater the attraction for electrons the greater
the energy released when an atom gains an electron.
ELECTRONEGATIVITY [EN]
• Electronegativity is a measure of the tendency of an
atom to gain electrons when it is chemically
combined (bonded) to another element.
• The stronger the ‘pull’ or attraction of electrons to an
atoms nucleus, the greater its tendency to gain
electrons
In general, metals have low EN and nonmetals have
high EN. The actual amount of EN an atom has is
indicated by a number of the Pauling Electronegativity
Scale that goes from 0 to 4. Dr. Linus Pauling set up
this scale and gave the element having the greatest EN
an arbitrary number of 4, and he assigned numbers to
the others relative to this element.
Trend: Electronegativity (EN)
Period trend - EN increases as you go across a period
(excluding the noble gases) because size decreases.
Group trend - EN increases as you go up a group because
there is less pull from the nucleus as the electrons get
further away.
Highest
Example
Electronegativity Trend
• Which would have the greater
EN? Ca or Se
Se
Electronegativity enables us to predict what
type of bond will be formed when two elements
combine.
Electronegativity Chart
Electronegativity Chart
Electronegativity Chart
Agenda
• Expanations of Trends and Summary
• Lesson: PPT
• Handouts: 1. Propeties of Atoms, 2. Trends in
the Periodic Table Summary Sheet
• Text: 1. P. 36-41-Trends parameters and
definitions
• HW: 1. P. 41 # 1-7; 2. Finish all the
worksheets
Reactivity of Nonmetals
Reactivity -how easily a substance reacts with another
• Nonmetals gain electrons ( Electron Affinity)
• Metals lose electrons ( Ionization Energy)
Highest
Metal Reactivity
Trend
Highest
Nonmetal Reactivity
Trend
TRENDS IN THE PERIODIC TABLE - SUMMARY SHEET
NAME
DEFINITION
TREND
Distance
1.
ATOMIC measured from Increases down
RADIUS the centre of the a group
nucleus to the
outermost e_ in
pm or Ao
2.
Decreases
across a period
from left to
right
EXPLANATION
1.
Increase in no. of
energy levels and
electrons -more
repulsion
2.
e- held more
tightly, increase in
ENC, less shielding
smaller radius
NAME
DEFINITION
TREND
Energy required 1.
FIRST
to remove the Decreases
IONIZATION outermost
down a group
ENERGY electron from a
gaseous atom
EXPLANATION
1.
Increase in radius
due to more
energy levels
,electrons less
tightly held
2.
2.
Increases
e- held tightly,
across a period increase in ENC
from left to
less shielding ,
right
harder to remove
e-
NAME
DEFINITION
TREND
The energy
1.
ELECTRON given off
Increases up a
AFFINITY (released)
group
when an atom
gains an e2.
Increases
across a
period from
left to right
not including
Group 18
EXPLANATION
1.
Fewer energy levels,
small atomic radius ...
greater attraction of
electrons
2.
Greater ENC, greater
attraction for
electrons, less
shielding
NAME
DEFINITION
TREND
The tendency 1.
ELECTRO- to gain
Increases up a
NEGATIVITY electrons
group
2.
Increases across
a period from
left to right not
including Group
18
EXPLANATION
1.
Fewer energy
levels, small atomic
radius ... greater
attraction of
electrons
2.
Greater ENC,
greater attraction
for electrons, less
shielding
NAME
DEFINITION
The degree to
REACTIVITY which metals
METALS have a
tendency to
react with
other
substances by
losing
electrons
TREND
EXPLANATION
1.
1.
Increases
More energy levels,
down a group larger atomic radius ...
weaker attraction of
e-electrons more easily
removed
2.
2.
Decreases
Lower ENC, weaker
across a
attraction for e-, less
period from shielding, more easily
left to right
removed
NAME
DEFINITION
The degree to
REACTIVITY which
NONMETALS nonmetals
have a
tendency to
react with
other
substances by
gaining
electrons
TREND
1.
Increases
up a group
EXPLANATION
1.
Fewer energy levels,
smaller atomic
radius ... greater
attraction of
electrons
2.
2.
Increases
Greater ENC, greater
across a
attraction for
period from electrons, less
left to right shielding
not
smaller atomic
including
radius
Group 18
Effective Nuclear Charge
Group
Number
Element
# of electrons
# of valance
electrons
# of protons
# of inner
electrons
ENC
1
2
Na
13
Mg
14
Al
15
Si
16
P
17
S
18
Cl
Ar
Effective Nuclear Charge
Group
Number
Element
# of electrons
# of valance
electrons
# of protons
# of inner
electrons
ENC
1
2
13
14
15
16
17
18
Na
Mg
Al
Si
P
S
Cl
Ar
11
12
13
14
15
16
17
18
1
2
3
4
5
6
7
8
11
12
13
14
15
16
17
18
10
10
10
10
10
10
10
10
Effective Nuclear Charge
Group
Number
Element
# of electrons
# of valance
electrons
# of protons
# of inner
electrons
ENC
1
2
13
14
15
16
17
18
Na
Mg
Al
Si
P
S
Cl
Ar
11
12
13
14
15
16
17
18
1
2
3
4
5
6
7
8
11
12
13
14
15
16
17
18
10
10
10
10
10
10
10
10
1
2
3
4
5
6
7
8
ENC = Number of Protons – Number of Inner Electrons
EFFECTIVE NUCLEAR CHARGE AND
SHIELDING
• The force of attraction between positively charged
protons in the nucleus and negatively charged electrons
is the force that holds atoms together.
• The inner electrons (not in the outermost energy level) in
inner energy levels, partially block or shield the
attraction of the protons from the outer electrons in the
outermost energy level (VALENCE ELECTRONS).
• The canceling of the positive nuclear charge is called
SHIELDING EFFECT.
EFFECTIVE NUCLEAR CHARGE
(ENC)
• EFFECTIVE NUCLEAR CHARGE (ENC) is a number assigned to
elements to describe the amount of shielding felt by the valence
electrons.
ENC = Number of protons - Number of inner electrons
• The greater the ENC the less the valence electrons are shielded and
the stronger the pull on the valence electrons.
• Greater ENC will mean a smaller atomic radius.
• Shielding will help explain some of the trends in the periodic table
Agenda
Successive Ionization Energies
• Lesson: PPT- Take up of all the problems
• Handouts: 1. Properties of Atoms, 2. Trends in
the Periodic Table Summary Sheet
• Text: 1. P. 36-41-Trends parameters and
definitions
• HW: 1. Finish all the worksheets 2. P 47 118; P. 48 #1-19,31; P. 48 # 47,55-57,65-69.
SUCCESSIVE IONIZATION ENERGIES
• The first ionization energy is the energy required to
remove the outermost electron (First IE). It is
relatively low because of the repulsion exerted by
the other electrons
• Each successive ionization energy (Second and Third
IE and so on) will increase.
• It becomes more difficult to remove successive
electrons since the pull of the nucleus becomes
stronger (greater number of protons relative to the
electrons) and the electrons are more tightly held
Ionic radius becomes smaller
• There will be a noticeable jump in the increase of IE
once the noble gas configuration has been reached
This is because outer energy level has been removed (
radius is smaller)
Successive Ionization Energies
Example 1: Consider the following Ionization Energies
for an element X:
How many valance electrons does this element have?
1st
2nd
3rd
4th
5th
2.38 kJ
2.54 kJ
22.48 kJ
25.88 kJ
28.35 kJ
ANS:
The element has 2 valence electrons. Removing the
third electron from X 2+ involves a much greater energy.
The third electron is closer (one energy level closer) to
the attracting nucleus since the noble gas configuration
has been reached.
Example 2: Where would the large increase in I.E. occur
for Se? Explain your answer.
The large increase would occur going form 6th to 7th IE.
There is a noticeable jump in increase of I.E. since the
noble gas configuration has been reached.
(Se 6+) 1s2 2s2 2p6 3s2 3p6