Transcript (blue) an isotope of the original element

Ganymede, the largest moon in the
Solar System (larger than Mercury
and Pluto), has a surface speckled
with bright young craters overlying
a mixture of older, darker, and more
cratered terrain laced with grooves
and ridges. The colors here have
been enhanced to increase surface
contrasts.
The violet shades extending from
the top and bottom are likely due to
frost particles in Ganymede’s polar
regions. Future missions to Jupiter
are being proposed that can search
Europa and Ganymede for deep
oceans that may harbor elements
thought important for supporting
life.
Homework #2 is due Wednesday
 Multiple choice portion: noon
 Short answer portion: class time
Homework #3 will be posted on Wednesday
It will be due Tuesday, Sept. 29, 5:00 pm
Exam #1, Wednesday, Sept. 30
Radiative energy:
energy carried by
electromagnetic
radiation (light).
Light
A vibration in an electromagnetic field
through which energy is transported.
Light as a wave
Light as a particle (photon)
Properties of Waves
WAVELENGTH (: Distance
between adjacent crests
FREQUENCY (f): number of crests that pass through a point
each second. It is measured in units of hertz (Hz), which are
the number of cycles per second.
AMPLITUDE: A measure of the strength of the wave.
SPEED (s): how fast the wave pattern moves.
For any wave:
s=f
Light as a Wave
• The speed of light is a constant: s = c !!!
• Therefore, for light:
f=c
• The higher f is, the smaller  is, and vice versa.
• In the visible part of the spectrum, our eyes recognize
f (or ) as color!
Light as a Particle
 Light can also be treated as photons – packets of energy.
 The energy carried by each photon depends on its frequency
(color)
 Energy:
E = hf = hc/  [“h” is called Planck’s Constant]
Shorter wavelength light carries more energy per photon.
The Electromagnetic Spectrum
lower
energy
higher
energy
Light as Information Bearer
Spectrum: light separated into its different wavelengths.
Spectroscopy: The quantitative analysis of spectra
The spectrum of an object can reveal the object’s:
Composition
Temperature
Velocity
“Matter” and Light
nucleus
Atom
electron
(proton,neutrons)
p+
n
●
●
●
e-
10,000,000 atoms can fit across a period in your textbook.
The nucleus is nearly 100,000 times smaller than the entire atom (if
atom filled the classroom auditorium, the nucleus would be barely
visible at its center).
Although it is the smallest part of the atom, most of the atom’s mass
is contained in the nucleus.
Electrons do not “orbit” the nucleus; they are “smeared
out” in a cloud which give the atom its size.
Incorrect
view
better
view
Periodic Table of
the Elements
atomic number = #protons (determines element)
atomic mass no. = #protons + #neutrons
Hydrogen
ep+
atomic number = 1
atomic mass number = 1
Helium
ep+p+
n n
eatomic number = 2
atomic mass number = 4
Hydrogen
Deuterium
isotope
of hydrogen
p+
n
atomic number = 1
atomic mass number = 2
e-
The particles in the nucleus determine
the element & isotope.
Atomic Number
1
2
3
4
5
6
7
8
Element
Hydrogen (H)
Helium (He)
Lithium (Li)
Beryllium (Be)
Boron (B)
Carbon (C)
Nitrogen (N)
Oxygen (O)
Relative abundances of
elements in the universe
Every element has multiple isotopes
(same number
of protons, different numbers of neutrons) some of which
may not be stable (“radioactive”)
Carbon-14 half-life
= 5,730 yrs
Unstable (“radioactive”) isotopes
“decay”, producing a new type of atom,
i.e., an atom of a different element, or a
different isotope of the original element.
One half of the atoms of an unstable
isotope decay in one “half-life” of that
isotope.
Three isotopes of Carbon, two stable, one unstable.
5730 yrs
14C
 14N + electron + antineutrino + energy
Mass (14C) > Mass (14N + electron + antineutrino)
 difference in mass is converted into energy: E = mc2
What if an electron is missing?
ion
ep+p+
n n
atomic number = 2
atomic mass number = 4
+1
He
What if two or more atoms combine to form a
particle?
molecule
H2O (water)
p+
Sharing of electrons
(chemistry) is
involved in the
construction of
molecules
8p+
8n
p+
If you added a proton to an atom to create a
new stable, isolated atom, you would have
created…
(blue) an isotope of the original element
(yellow) a fission reaction
(red) a different element with a positive charge
(green) a neutron and a positron
If you added a proton to an atom to create a
new stable, isolated atom, you would have
created…
(blue) an isotope of the original element
(yellow) a fission reaction
(red) a different element with a positive charge
(green) a neutron and a positron
If you removed an electron from an atom, you
would have created
(blue) an isotope of the original element
(yellow) a fission reaction
(red) a different element with a positive charge
(green) an ionized atom
If you removed an electron from an atom, you
would have created
(blue) an isotope of the original element
(yellow) a fission reaction
(red) a different element with a positive charge
(green) an ionized atom
If you combined two atoms such that they
shared electrons to create a new stable object,
you would have created
(blue) an isotope of the original element
(yellow) a molecule
(red) a different element
(green) an ionized atom
If you combined two atoms such that they
shared electrons to create a new stable object,
you would have created
(blue) an isotope of the original element
(yellow) a molecule
(red) a different element
(green) an ionized atom
Four Ways in Which
Light can Interact with Matter
1.
emission – matter releases energy as light
2.
absorption – matter takes energy from light
3.
transmission – matter allows light to pass through it
4.
reflection – matter reflects light
The type of interaction is determined
by characteristics of the “matter” and
the wavelength of light.
Different
wavelengths
of light
interact
differently
with the
atmosphere
Three ways in which spectra manifest
themselves:
 Continuous spectra
 Absorption spectra
 Emission line spectra
 Continuous spectra
are usually related to the
temperature of an object that is
emitting radiation.
 Absorption & emission
line spectra are related to the
composition of the material
absorbing or emitting radiation.
Kirchhoff’s Law #1
1. A hot, dense glowing object (solid or
gas) emits a continuous spectrum.
Rules for Thermal Emission by Opaque Objects
1. Hotter objects emit
more total radiation
per unit surface area.
2. Hotter objects have
their peak radiation
at shorter
wavelengths (they
will appear “bluer”)
The sun emits its peak radiation in the
yellow portion of the visible spectrum
At “room temperature”, or “bodytemperature”, an object emits its peak
radiation in the infrared.
Which of the two stars (A or B) emits light that has a
peak emission with the longer wavelength?
(red) Star A
visible
range
(green) The stars’
peak emissions are at
the same wavelength
(yellow) None of the
above
Energy output per second
(blue) Star B
A
B
VIBGYOR
Wavelength
Which of the two stars (A or B) emits light that has a
peak emission with the longer wavelength?
(red) Star A
visible
range
(green) The stars’
peak emissions are at
the same wavelength
(yellow) None of the
above
Energy output per second
(blue) Star B
A
B
VIBGYOR
Wavelength
Which of the two stars (A or B) would appear red?
(red) Star A
visible
range
(green) Neither would
appear red
(yellow) There is
insufficient
information to
determine the star’s
color
Energy output per second
(blue) Star B
A
B
VIBGYOR
Wavelength
Which of the two stars (A or B) would appear red?
(red) Star A
visible
range
(green) Neither would
appear red
(yellow) There is
insufficient
information to
determine the star’s
color
Energy output per second
(blue) Star B
A
B
VIBGYOR
Wavelength
The figure shows the spectra of two stars.
Which star is hotter?
visible
range
(blue) C
(yellow) neither
Energy output per second
(red) A
A
C
VIBGYOR
Wavelength
The figure shows the spectra of two stars.
Which star is hotter?
visible
range
(blue) C
(yellow) neither
Energy output per second
(red) A
A
C
VIBGYOR
Wavelength
Which of the following is possible to infer about stars A
and C based upon the information provided in the graph?
(red) Star A is
smaller than star C
(green) The stars
are the same size
(yellow) It is not
possible to infer
any of these
relationships
Energy output per second
(blue) Star A is
larger than star C
visible
range
A
C
VIBGYOR
Wavelength
Which of the following is possible to infer about stars A
and C based upon the information provided in the graph?
(red) Star A is
smaller than star C
(green) The stars
are the same size
(yellow) It is not
possible to infer
any of these
relationships
Energy output per second
(blue) Star A is
larger than star C
visible
range
A
C
VIBGYOR
Wavelength