Final Exam Flashcards
What is a “valence shell”?
The outer shell of electrons in an atom, where it meets and combines with other atoms.
The atomic number of Magnesium (Mg) is 12. Tell how many protons, neutrons and
electrons there are in one atom of 25Mg++. How many electrons are in that atom’s
valence shell? Explain your reasoning.
Since the atomic number is 12, that is the number of protons. Since the atomic mass is 25, which is equal
to the total number of neutrons and protons, there must be 25-12 = 13 neutrons in this isotope. An
electrically neutral atom has the same number of protons as electrons. Since this atom is a double-positive
ion, it must have two more protons than electrons, and therefore has only 10 electrons. Finally, since there
the first two electrons fill the first shell, there are eight to fill the outer, valence shell.
What are the three major ways atoms bond to form molecules? Give a brief explanation
of each.
In an IONIC bond, atoms that lose or gain electrons to have full valence shells will then become ions, and
may stick together electrostatically. In COVALENT bonds, two or more atoms fill their valence shells by
sharing electrons. A special type of this is the METALLIC bond, in which the electrons are passed around
and shared by all the atoms in the material.
Explain what an isotope is, and what an ion is.
Atoms of the same element which differ in the number of neutrons they have are known as “isotopes” of
that element. “Ions” are atoms which have an unequal number of protons and electrons.
What is a “half-life”?
It is the empirically determined length of time it takes for half of the population of something to disappear
or transform.
List the four fundamental forces, from weakest to strongest.
Gravity, Weak Force, Electromagnetic Force, Strong Force
What is a star?
A large ball of plasma (or gas) that radiates energy into space through fusion reactions powered by gravity
What is going to happen to our Sun?
It will complete its hydrogen-burning phase in a few billion years, enter into a “helium-burning” phase,
turn into a Red Giant, and then into a White Dwarf. Eventually, billions more years later, it will cool into a
chunk of mostly carbon.
Briefly describe the Milky Way galaxy
It is a spiral galaxy consisting of about 100 billion stars, about 100,000 ly across, with a central bulge
known as the nucleus, and bright regions (spiral arms) where new stars are being formed.
List at least three facts that serve as evidence for the Big Bang.
- Universal expansion, 2. Cosmic microwave background radiation, 3. Abundance of light elements, 4.
Lack of antimatter. 5. Hubble’s constant, 6. The darkness of the night sky (Olber’s paradox).
According to current science, what is the likely fate of the universe?
Even counting dark matter, we estimate that only about 20% of the mass necessary to slow down the
expansion of the universe exists. In fact, recent (1999) observations indicate that the expansion might
actually be speeding up. We probably live in an “open” universe, which means it will expand forever,
cooling as it does, eventually to absolute zero. Sometimes called “Heat Death.”
What is the Nebular Hypothesis, and what evidence exists for it?
About 4.5 billion years ago, a large, rotating cloud of gas coalesced under gravitational attraction to form
small chunks of material called planetesimals. These collided with each other to produce larger and larger
objects. Most of the mass, however, coalesced in the center to produce the Sun. Evidence for this is (1) the
difference between the inner (terrestrial) planets, which are small rocky worlds and the outer (Jovian)
planets, which are large balls of frozen gas, essentially the same as the original nebular medium, (2) the
planets revolve around the sun in the same direction as its rotation (3) most of the planets rotate on their
axes in the same direction as the sun’s rotation, (4) the plane of revolution of most of the planets is within
about 5° of the ecliptic. It’s hard to believe that all this is just a coincidence!
Explain the three basic types of plate boundaries
(1) Divergent, in which two plates are moving away from each other, (2) Convergent, in which they are
pressing against each other, and (3) Transform, in which they are scraping alongside each other.
Explain what S and P waves are and tell why the difference between them matters to
seismologists.
These are some of the waves that are produced by earthquakes. P waves are “primary” waves, formed from
the Earth shaking up and down. They are longitudinal in nature, and therefore can travel through the
Earth’s liquid outer core. They are faster than S waves, and so are the first to arrive at a detection station.
S waves (“secondary”) are caused by the surface moving back and forth, are transverse, and cannot travel
through the outer core. They arrive later and have magnitudes different from the P waves. These features
allow for the calculation of the earthquake’s magnitude and point of origin (“epicenter”).
Give the names of at least six of Earth’s tectonic plates.
African Anatolian Antarctic Arabian Australian-Indian Caribbean Cocos Eurasian Hellenic Iranian Juan de Fuca Nazca North American Pacific Philippine Scotia South American
Explain the “First Principle of Science”
It may be stated as “There exists an objective reality,” and means essentially that at least some of the
features of reality are as they are independently of what we might believe. It deserves primacy of place
because, unless science and scientists believe that, there can be no investigation into the physical world, no
learning.
Write the equation for a graphed line, and explain its terms.
Y=mx +b. Y is the value of the dependent variable (vertical axis), x the value of the independent variable
(horizontal axis), m is the slope of the line (rise/run or dy/dx), indicating the rate of change, and b is the “yintercept” where the line crosses the y-axis (x=0).
What are the three different ways in which heat is transferred?
- conduction
- convection
- radiation
Explain the difference between longitudinal waves and transverse waves, and give an
example of each.
In T-waves, the motion of the wave itself is different from (perpendicular to) the motion of the medium in
which the wave moves. For example, waves in water move across the surface of the water, while the water
itself merely moves up and down.
In L-waves, the wave moves in the same direction as the medium through which it moves. Sound waves,
for example, are created by moving air molecules back and forth, which then collide with neighboring
molecules, inducing them to continue the process.
What features are shared by all electromagnetic waves? In what ways might two such
waves differ?
They all travel at the speed of light and the need no medium through which to travel. They can differ
according to wavelength and frequency (and therefore energy).
What is the difference between “special” relativity theory and “general” relativity
theory?
Special relativity deals with observers who are not accelerating with respect to each other, while general
relativity deals with any frame of reference whatsoever
What, according to special relativity, happens to my alarm clock when I throw it across my room in
the morning? Will I be able to observe these effects?
Its mass increases, it gets shorter in the direction it is traveling, and it keeps time more
slowly. None of these effects are observable unless the object is traveling at “relativistic”
speeds, i.e., speeds that are a significant fraction of the speed of light, so I won’t notice
anything. I’ll feel a lot better, though.
What is “wave-particle duality”?
Every quantum particle (atom-sized or smaller) exhibits qualities of waves or particles, depending upon
how they are observed.
What two important features of “chemistry” is it important to know?
- Chemistry takes place in the outer (“valence”) shells of atoms.
- A significant portion of the characteristics of the resulting molecule is determined by its physical shape
