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Transcript
Energy and Periodic Trends
Unit: Energy and Periodic Trends
Topic: Periodic Table Trends
Objectives: Day 1of 2
• To understand the types of radiation
• To learn about ionization energy and how it
relates to the periodic table
• To learn about electronegativity and how it
relates to the periodic table
Quickwrite
Answer one of the questions below 1-2
sentences:
• If you recall, which group of the periodic table
readily gives up electrons to form cations??
• If you recall, which group of the periodic table
readily gains electrons to form anions??
Atomic Properties
• Science is based on observations and discoveries
• For example, certain observations about substances
will help us better understand our world
• We know that wood burns, steel rusts, plants grow,
and sugar tastes sweet
• A better understanding of how atoms and molecules
behave is crucial to helping us explore our natural
world
• The periodic table is an important tool in helping us
understand why atoms have predictable
characteristic properties
• The objective is to understand the general trends or
patterns in atomic properties in the periodic table
Metals, Semimetals, &
Nonmetals
• If you recall, the
periodic table is
divided into 3 basic
different types of
elements:
-Metals
-Semimetals
-Nonmetals
Metals
Semi Metals
Nonmetals
Atomic Properties & the Periodic Table
1+ Cations 2+ Cations 3+ Cations 2- Anions 1- Anions
If you recall, group 1 metals like to lose an electron and group 2
metals like to lose an two electrons, becoming positively charged
Non metals on the other hand, like to gain
electrons and become negatively charged
Atomic Properties & the Periodic Table
Lithium is the least
likely to lose an electron
Cesium loses an
electron most easily
But what elements in group 1 are the most likely to lose an electron?
Not all metals in group 1 behave exactly the same way
For example, some metals can lose one or more
electrons much more easily than others
Cesium at the bottom of group 1, gives up an electron
much more easily than lithium at the top of group 1
Atomic Properties & the Periodic Table
In fact, as we go down the periodic table, the metals in
group 1 become more likely to lose an electron
Cs
> Rb
>
K
>
Na
>
Li
Cesium loses an
electron most easily
Lithium is the least
likely to lose an electron
Group 1
Atomic Radius (Size)
Period 4
What do you notice
about
relative
What do
you the
notice
aboutsizes
the of
the
atoms
as we
move up
group as
1? we mov
relative
sizes
of period
4 atoms
That’s right
the atomic
radius
gets
across
the periodic
table
leftsmaller!
to right?
That’s right the atomic radius gets small
Atomic Radius (Size)
Atomic Size
Decreases
Atomic Size
Decreases
Atomic Size
Li
Na
K
Atomic Size
Decreases
Rb
• What makes the atomic
size get bigger?
• Their nucleus and
electron cloud size
becomes larger
Atomic Size
Decreases
Cs
Na
Mg
Al
Si
P
S
Cl
Ar
How does atomic Size Change
across the Periodic table?
decreases as we go
• Atomic size ________
Decreases
up the periodic table and
decreases as we go left to right
• Their nucleus and electron cloud
larger
gets ________
Decreases
• Draw:
Answer Bank
Weakly
larger
Attract
remove
Decreases
low
Ionization Energies
• The ionization energy is the energy
required to remove an electron from an
individual atom
• Think of it as how easily an atom loses an
electron
• Metals have low ionization energies, and
nonmetals tend to have higher ionization
energies
Sodium (Na) Atom
e-
How much energy
is required to remove an
electron from a sodium
atom?
1+
e-
e-
e-
e-
Recall that sodium
likes to lose an
electron to form a +1 ion
P+
NNP+P+
NP+
P+
N
P+P+
P+
N
eN
NP+
P+
P+NP+
e-
In general, metals
such as sodium have
low ionization energies?
e-
e--
e-
Na + energy Na+1 + e
ee-
e-
Ionization Energy
Ionization
Energy Increases
Ionization
Energy Increases
What
do you
aboutEnergy
the relative
Notice
thenotice
Ionization
trend sizes of
the atoms as we move up from cesium to Lithium?
What is Ionization Energy?
• The energy required to ______
remove an
electron from an individual atom
• Metals (group 1 & 2) have _____
low
ionization energies and nonmetals
(group 17 halogens & group 18
noble gases) have high ionization
energies
Increases
• Draw:
Answer Bank
Weakly
larger
Attract
remove
Decreases
low
Increases
Electronegativity
• If Ionization energy is how easily an atom loses
an electron, then think of electronegativity as the
exact opposite
• Electronegativity is the ability of an atom to
attract electrons
• Think of it as the liking or attraction an atom has
for an electron
• Nonmetals such as Flourine, chlorine and
oxygen have high electronegativities
• In other words, Flourine, Chlorine and Oxygen
love to steal electrons form other atoms
Electronegativity
Electronegativity
Increases
Electronegativity
increases
What
do you
about the relative
Notice
thenotice
Electronegativity
trend sizes of
the atoms as we move up from cesium to Lithium?
What is
Electronegativity?
The ability of an atom to _______electrons
attract
•
• Think of it as the attraction an atom has for
Answer Bank
an electron
Weakly
larger
• Nonmetals such as Fluorine, Chlorine and
Attract
Oxygen have high electronegativities along
remove
with noble gases such as Helium and
argon
Increases
• Draw:
Decreases
low
Increases
Electronegativity vs. Ionization Energy
• What determines Ionization energy and
Electronegativity? The answer is atomic radius!
P+
NNP+P+
NP+
P+P+NP+
P+
NN
NP+
P+P+
NP+
e- atoms lose
Larger
Electrons easier
because the outer
electrons are
farther from the
nucleus, & are therefore
more weakly held
Electronegativity vs. Ionization Energy
• What determines Ionization energy and
Electronegativity? The answer is atomic size!
P+
NNP+P+
NP+P+
e- P+
P+ N
P+
NN
NP+
P+P+
NP+
Smaller atoms like fluorine hold
their outer electrons are closer
to the Nucleus and therefore
e- do not Lose their electrons
as easy
This also enables them to steal
Electrons from other atoms
(High electronegativity)
The more Electronegative Atom, Fluorine in this case,
steals the weakly held outer electrons from Cesium
NNP+P+
NP+
P+P+e- P+
N
P+
P+
N
N P+
NP+
P+
P+N
e-
P+
NNP+P+
NP+
N
P+P+ P+
P+
N
N P+
NP+
P+
P+N
Fluorine
Cesium
e-
How does atomic size effect ionization
energy and electronegativity?
• Larger atoms (cesium) with low
ionization energies weakly
______ hold
their outer electrons and therefore
easily lose them
• Smaller atoms (fluorine) with high
electronegativities strongly hold
their electrons closer to the nucleus
and therefore steal electrons from
other atoms
Answer Bank
Weakly
larger
Attract
remove
Decreases
low
Summarize:
• List 3 atoms with a large atomic radius:
• Explain where atoms with low ionization
energies can be found: List 3 examples:
• Explain where the most electronegative
atoms can be found: List 3 examples:
• Explain where the largest atomic size can
be found on the periodic table:
Unit: Light & Periodic Trends
Topic: Energy and Light
Objectives: Day 2 of 2
• To understand different properties of light
such as wavelength and frequency
• To understand how light is given off on the
atomic level
Quickwrite
Answer one of the questions below 1-2
sentences:
• How do you think atoms give off light????
• What is radiation??? What are some different
forms of radiation you might have heard of????
Energy and Light
• If you hold your hand a few inches from a
brightly glowing light bulb what do you feel?
• Your hand gets warm!
• The light from bulb somehow transmits
energy to your hand
• The same thing happens when you move
close to the glowing embers of wood in a
fire place
• The energy you feel from the sun is a
similar example
Energy and Light
• In all 3 of these examples, energy is
being transmitted from one place to
another by light—more properly called
electromagnetic radiation
• Many kind of electromagnetic radiation
exist, including x-rays, used to penetrate
your skin and produce images of your
bones, microwaves to cook your food,
and radio waves so you can call a friend
on your cell phone
What is electromagnetic
radiation?
• Energy transfer in the form
of_______
waves
• Examples include: light, x-rays,
radio waves, infrared (heat)
waves
Answer Bank
Between
Time
excited
packet
Waves
ground
Energy and Light
• How do these various types of
electromagnetic radiation differ from
one another? To answer this question
we need to talk about waves
• Waves are characterized by 3
properties: wavelength, frequency and
speed.
• The wavelength symbolized by the
symbol lamda (λ)
• It is the distance between 2
consecutive wave peaks
Energy and Light
• How do these various types of electromagnetic
radiation differ from one another? To answer
this question we need to talk about waves
• Waves are characterized by 3 properties:
wavelength, frequency and speed.
• The wavelength symbolized by the symbol
lamda (λ)
• It is the distance between 2 consecutive wave
peaks
λ
What is wavelength?
• The distance ________
between 2
consecutive wave peaks
Answer Bank
Between
Time
excited
packet
Waves
ground
Energy and Light
• The frequency of a wave (symbolized by
the greek letter nu, ν) indicates how many
times a peak passes by a point for a given
time period
• Think of it as how many times the blue
circle goes up and down every minute
What is the frequency?
• The frequency of a wave
(symbolized by the greek letter nu,
ν) indicates how many times a peak
passes by a point for a given _____
time
period
• (Think of it as how many times the blue circle
goes up and down every minute)
Answer Bank
Between
Time
excited
packet
Waves
ground
Energy and Light
• Light waves, x-rays, radio waves are all
classified based on their wavelength
• Notice that x-rays have very short
wavelengths, where as microwaves and
radio waves have very long wavelengths
Radiation Link
• http://www.classzone.com/books/earth_sci
ence/terc/content/visualizations/es2601/es
2601page01.cfm?chapter_no=visualizatio
n
Energy and Light
• The interesting thing about
electromagnetic radiation is that it doesn’t
always behave like as though it were a
wave
• Sometimes electromagnetic radiation can
have properties that are characteristic of
particles
Energy and Light
• Another way to think of a beam light
traveling through space is as a stream of
tiny packets of energy called photons
What is photon?
Packet
• A “particle or _______
of
energy” of electro magnetic
radiation
Answer Bank
Between
Time
excited
packet
Waves
ground
Energy and Light
So what is the exact nature of radiation
and light?
• Is it a particle or wave? It seems both
• This situation is often referred to as the
wave-particle nature of light
Energy and Light
• Different wavelengths of electromagnetic
radiation carry different amounts of energy
• Shorter wavelengths carry less energy than
longer wavelengths Is it a particle or wave? It
seems both
Energy levels of Helium
• An atom that it is excited can release
energy in the form of light or photons
• An atom that is not excited is said to be in
it’s ground state rather than it’s excited
state
eHelium Atom
e-
Excited State
Ground State
(high energy level) (low energy level)
P+ N
N P+
e-
e-
How does an atom
give off light?
• An atom absorbs energy and
becomes “_________”
excited
• The electrons are now in an excited
state (higher energy level)
• As electron return to their ______
ground
state (low energy level), they give off
light or photons
• The type of light (red or blue light)
being emitted is dependent upon the
difference in energy between the
ground and excited states
Answer Bank
Between
Time
excited
packet
Waves
ground
Summarize:
• List 3 different types of radiation:
• What’s the difference between wavelength
and frequency:
• How is a photon different from a wave?
• In your own words, explain how light is
given off on the atomic level:
Can I Remove More Than One
Electron?
• A second, third, etc, electron can be
removed from an atom.
• The ionization energies are termed
accordingly:
– 2nd Ionization energy to remove the 2nd
electron.
– 3rd Ionization energy to remove the 3rd
electron.
ns2np6
ns2np5
ns2np4
ns2np3
ns2np2
ns2np1
d10
d5
d1
ns2
ns1
Ground State Electron Configurations of the Elements
4f
5f
8.2