CEM 141 Final Exam |48 Accurate Q’s
and A’s
Why are alpha particles deflected by the nucleus? - -Because both the alpha
particles and the nucleus are positively charged and so the alpha particle is
repelled.
- Is this statement (Dalton's Theory) true or false and why?
"All atoms of an element are identical and have the same mass and
properties." - -False.
Atoms of the same element can have different numbers of neutrons.
- What is the evidence that electrons are subatomic particles? - -The nature
of the electron is independent of the material from which it emerges.
- Example of a theory (explains) - -The properties of matter can be
EXPLAINED by understanding that matter is composed of atoms that interact
and move in various predictable ways.
- Why is the boiling point of iodine higher than that of bromine? - -Because
iodine has a larger more polarizable electron cloud. The electrostatic
attraction between the iodine molecules requires more energy to overcome.
- When bromine melts, what is happening? - -Attractive forces between
molecules are overcome.
- When oxygen freezes, what is happening with the forces and energy
changes during this process? - -New LDFs are formed. Energy is released to
the surroundings. Energy is transferred via collisions.
- Where would two atoms of He be most stable on a PE curve? - -The PE
well, where the attractive and repulsive forces are equal and the system is
most stable.
- For a pencil sitting on a desk, what forces are acting upon the pencil? - -
Both gravitational and electrostatic.
- If the PE increases as two particles approach, what are they most likely? -
-Two protons (positively charged/same charge).
- How do atoms know that temperature is increasing? - -Thermal energy is
transferred upon collision with other atoms.
, - What two atoms would have the greatest gravitational forces? Two 10g
separated by 10 meters. Or, one 100g and one 1g separated by 5 meters?
m1m2/r^2 - -100g and 1g separated by 5 meters.
(100)(1)/(25) = 4
- In the solid state, atoms of xenon are held together by.. - -London
Dispersion Forces ONLY because Xenon is a noble gas that cannot bond
together.
- What does a lower PE well mean?
What does a further right position on the PE graph mean? - -More energy
needed to break interactions.
Longer bond.
- What is true about the PE minimum for the approach of two atoms? - -The
depth of the well tells you how much energy is required to break an
interaction.
- In breaking a single chemical bond.. - -Energy is RELEASED.
- As two atoms approach each other why does the PE decrease? - -Because
there is an attractive force between the two atoms.
- What does not have atoms in it? - -Light and heat.
- What subatomic particle was discovered last? - -The neutron because it
has no charge and is therefore difficult to detect.
- Can you have an atom of a compound? - -NEVER.
- What does atomic radius do from left to right across a row on the Periodic
Table? - -Decreases because the relative attraction between the protons and
the outer electrons increases.
- What is the relationship between the energy and frequency? - -Positive
linear. As energy increases, the frequency increases.
- Why do we use an energy level diagram rather than the Bohr model of the
atom to describe electron behavior in atoms? - -Energy level diagrams
describe electron behavior of all elements and the Bohr model only describes
hydrogen. Energy level diagrams do not imply distance from the nucleus but
the Bohr model does.
- Will an electron be emitted below a substances minimum frequency? - -
NEVER.
and A’s
Why are alpha particles deflected by the nucleus? - -Because both the alpha
particles and the nucleus are positively charged and so the alpha particle is
repelled.
- Is this statement (Dalton's Theory) true or false and why?
"All atoms of an element are identical and have the same mass and
properties." - -False.
Atoms of the same element can have different numbers of neutrons.
- What is the evidence that electrons are subatomic particles? - -The nature
of the electron is independent of the material from which it emerges.
- Example of a theory (explains) - -The properties of matter can be
EXPLAINED by understanding that matter is composed of atoms that interact
and move in various predictable ways.
- Why is the boiling point of iodine higher than that of bromine? - -Because
iodine has a larger more polarizable electron cloud. The electrostatic
attraction between the iodine molecules requires more energy to overcome.
- When bromine melts, what is happening? - -Attractive forces between
molecules are overcome.
- When oxygen freezes, what is happening with the forces and energy
changes during this process? - -New LDFs are formed. Energy is released to
the surroundings. Energy is transferred via collisions.
- Where would two atoms of He be most stable on a PE curve? - -The PE
well, where the attractive and repulsive forces are equal and the system is
most stable.
- For a pencil sitting on a desk, what forces are acting upon the pencil? - -
Both gravitational and electrostatic.
- If the PE increases as two particles approach, what are they most likely? -
-Two protons (positively charged/same charge).
- How do atoms know that temperature is increasing? - -Thermal energy is
transferred upon collision with other atoms.
, - What two atoms would have the greatest gravitational forces? Two 10g
separated by 10 meters. Or, one 100g and one 1g separated by 5 meters?
m1m2/r^2 - -100g and 1g separated by 5 meters.
(100)(1)/(25) = 4
- In the solid state, atoms of xenon are held together by.. - -London
Dispersion Forces ONLY because Xenon is a noble gas that cannot bond
together.
- What does a lower PE well mean?
What does a further right position on the PE graph mean? - -More energy
needed to break interactions.
Longer bond.
- What is true about the PE minimum for the approach of two atoms? - -The
depth of the well tells you how much energy is required to break an
interaction.
- In breaking a single chemical bond.. - -Energy is RELEASED.
- As two atoms approach each other why does the PE decrease? - -Because
there is an attractive force between the two atoms.
- What does not have atoms in it? - -Light and heat.
- What subatomic particle was discovered last? - -The neutron because it
has no charge and is therefore difficult to detect.
- Can you have an atom of a compound? - -NEVER.
- What does atomic radius do from left to right across a row on the Periodic
Table? - -Decreases because the relative attraction between the protons and
the outer electrons increases.
- What is the relationship between the energy and frequency? - -Positive
linear. As energy increases, the frequency increases.
- Why do we use an energy level diagram rather than the Bohr model of the
atom to describe electron behavior in atoms? - -Energy level diagrams
describe electron behavior of all elements and the Bohr model only describes
hydrogen. Energy level diagrams do not imply distance from the nucleus but
the Bohr model does.
- Will an electron be emitted below a substances minimum frequency? - -
NEVER.
