Chapter 3 Flashcards by Amelia D

________
13.8 Billion years ago – singularity
________ – rapid expansion of Universe

Big Bang

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Following the Big Bang
- 1 ________ after – no atoms, only leptons (electrons) and quarks
- 1 ________ after – protons and neutrons
- Few ________ after – H+ D+ He2+ Li3+ (density of air)
- For _______ years temp dropped as the Universe expanded – no further fusion occurred
- Then, electrons combined with nuclei to give atoms
- After _______ years, matter began to clump together and stars were formed (we’ll get to that)

Picosecond, microsecond, minutes, 380K, a billion

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Everything in the Universe is …

Moving away from us with increasing speed

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If an object emitting light is moving away from us, which direction will the wavelength of light be shifted?
1. To longer wavelengths
2. To shorter wavelengths
3. Toward the red end of the spectrum
4. Toward the blue end of the spectrum
5. It will not be shifted
A. 1 and 3
B. 1 and 4
C. 2 and 3
D. 2 and 4
E. 5 only

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Spectra of elements are more ______ shifted the farther away they are.

Red

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We can extrapolate backwards in time and, at some point in the past, we see all the matter and energy in the universe concentrated at one point (________).

singularity

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_____________
- Universe is expanding (red shift)
- Computer Models
- CMBR (cosmic microwave background radiation)
- 1.9 mm (microwave) radiation – relic of early Universe when electrons and protons were “recombining” into hydrogen atoms

Evidence of the Big Bang

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_____________
- Involve rearrangements (sharing, donating or accepting) of valence electrons.
- The identity of the element undergoing a chemical reaction does not change (EVER).

Chemical Reactions

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_____________
- Involve nucleus (not electrons).
- Often result in change in element (since element is defined by the number of protons).

Nuclear Reactions

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A
Fe
B
A:
B:

A: Mass number
B: Atomic number

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Which element has an atomic number of 19?
A. F
B. K
C. Na
D. Br

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How many protons and neutrons does 12^(N) have?
A. 6p, 6n
B. 7p, 5n
C. 5p, 7n
D. 7p, 7n

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Isotopes have the same # of _______ and a different # of _______.

Protons, neutrons

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Which is an isotope of 12^(C)?
A. 13^C
B. 12^(N)
C. 12^(Mg)

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(Types of Nuclear Reactions)
- ________ (adding two nuclei together)
- ________ (breaking a nucleus apart)
- ________ (emitting particles, α, β, γ etc)

Fusion, fission, radioactive decay

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At very high temperatures ________ can occur.

Nuclear fusion

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At very high temperatures, electrons on atoms are stripped away (they have so much energy that they can overcome the attraction to the nucleus) resulting in a …

Plasma

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As two nuclei move toward each other (but are still separated by distances greater than the size of the nucleus) what force affects them?
A. Electrostatic
B. Gravity
C. Strong nuclear
D. Weak nuclear

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As two nuclei move toward each other (but are still separated by distances greater than the size of the nucleus) what happens to the potential energy of the system?
A. Increases
B. Decreases
C. Stays the same

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If there is enough kinetic energy in the system (eg by heating it), the nuclei can get really close together. At that point the _________ comes into play.

Strong nuclear force

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To for atoms to get really close, a great deal of energy is required to overcome the _________ between the nuclei.

Electrostatic repulsion

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As two nuclei move very close together (at distances less than the size of the nucleus), the strong nuclear force comes into effect. What happens to the potential energy of the system?
A. Increases
B. Decreases
C. Stays the same

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Nuclear reactions are accompanied by changes in …

Mass

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The mass of the individual nucleons is greater than the mass of the …

Nucleus

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What happened to the mass of the nucleons that was lost when they combined to form a nucleus? What is it quantified as?

It was converted to binding energy, E=mc^2

E = mc^2 E = (mass in kg) × (3.00 × 10^8 m/s)^2 E = kg·m^2·s^-2 1 J = 1 kg·m^2·s^-2

Mass loss converted to binding energy

The energy released from nuclear reactions is ________ than from chemical reactions.

Much greater

Each deuterium atom is formed from 1 proton, 1 neutron, and 1 electron. How much energy is released by the formation of 1 deuterium (D) atom? Useful Info: E = mc^2 Mass defect: 0.00238 amu 1 amu = 1.6606 × 10^–27 kg c = 3.00 × 10^8 m/s 1 J = 1 kg·m^2·s^-2

3.56 x 10^-13 (kg x m^2 x s^2)

Each deuterium atom is formed from 1 proton, 1 neutron, and 1 electron (3.56 x 10^-13 J). How much energy is released by the formation of 1 mole of deuterium (D) atoms?

2.14 x 10^8 kJ/mol

It takes a lot of _______ to start a fusion reaction.

Energy

Slide 49 and 50

___________ is the fragmentation of heavy nuclei to form lighter, more stable ones + energy.

Nuclear Fission

Nuclear fission chain reactions can be used for ____________ (or __________).

Nuclear energy generation, nuclear bombs

__________ is the mass of the isotope required for the chain reaction to become self-sustaining.

Critical mass

___________ Nucleus emits or captures particles or energy in the form of electromagnetic radiation.

Radioactivity

____________ - Alpha particle emission - Beta particle emission - Electron emission - Positron emission - Electron capture - γ electromagnetic radiation

Common types of radioactivity

Do isolated atoms or molecules exist in a state (solid, liquid or gas)? A. Yes B. No

Do isolated atoms or molecules have melting points or boiling points? A. Yes B. No

States of matter, boiling points, and melting points are …

Emergent properties

When atoms interact to form larger collections, they have …

Emergent properties

__________ belong to a collection, but not the individual components.

Emergent properties

If a solid reacts with a gas, what state of matter will the product be? A. Solid B. Liquid C. Gas D. Part solid, part gas E. We cannot tell from the information given

The properties of any substance depend on the ________________ that exist within that substance.

Arrangement of atoms

The _________ of a substance depend on the bonding/interactions within that substance.

Properties

________ and ________ have similar causes (electrostatic attraction of the electrons of one atom to the nucleus of another).

LDF, covalent bonds

_____________ The magnitude of the attraction and how the electrons are arranged in the new species (which is formed by the interaction).

The difference between LDF and covalent bonds

Why do bonds form between atoms? A. Because atoms want to share electrons. B. Because atoms need to have a full octet. C. Because valence electrons are attracted to the nuclei of other atoms. D. Because the potential energy is at a minimum.

__________ electrons from one atom become attracted to the other nucleus.

Valence

_________ is most stable distance between the atoms - ie lowest potential energy.

Bond length

When bonds form energy is …

Released into the surroundings

Bonding Theories: Just like we have different atomic theories – we also have models of bonding. 1. 2.

Molecular Orbital Theory, Valence Bond Theory

Recall that electrons are ______ and can therefore combine constructively and destructively.

Waves

In _____ Theory, n atomic orbitals combine to give n molecular orbitals.

Molecular Orbital (MO) Theory When atomic orbitals combine constructively, _____________ form.

Bonding molecular orbitals

Bonding MOs are ________ energy than the atomic orbitals.

Lower

Molecular Orbital (MO) Theory Electrons in bonding orbitals make the species ...

More stable

Molecular Orbital (MO) Theory When atomic orbitals combine destructively, _____________ form.

Antibonding molecular orbitals

Antibonding orbitals are ________ energy than the atomic orbitals.

Higher

Electrons in antibonding orbitals make the species _________.

Less stable

Atomic orbitals can also combine destructively to form a molecular orbital of ...

Higher energy

Atomic orbitals can combine constructively (recall electrons can be considered as waves) to form a molecular orbital of ______ energy.

Lower

Both bonding and antibonding orbitals are in the same place in space – just at different ...

Energies

A bond will form if…

There are two electrons in a bonding molecular orbital

If there are also two electrons in an antibonding orbital, this cancels out the stabilization from two electrons in bonding orbital and, therefore ...

No bond forms

To break the bond, enough energy has to be added to ...

Raise an electron to the anti-bonding orbital

If we combine 2 atoms with 9 atomic orbitals each, how many molecular orbitals will result? A. 2 B. 4 C. 9 D. 18

When two O atoms interact, how many molecular orbitals are generated by the atomic orbitals in the core and valence shells? (Hint: Write the electron configuration for O.) A. 2 B. 4 C. 6 D. 10

How many bonds form between two O atoms? A. 0 B. 1 C. 2 D. 3 E. 4

As the number of MOs increases, the energy gap between them ...

Decreases

Bonding in Metals As the number of MOs increases, they form bands of MOs of ...

Almost continuous energy

Bonding in Metals Electrons can ________ between MOs.

Move freely

Bonding in Metals Electrons can ________ over whole system.

Move freely

Properties of Metals _______________ will promote an electron to a higher energy level.

Absorption of a photon

Properties of Metals The metal interacts with _________, so the metal appears white or colorless (silvery).

Light of many wavelengths

Why are metals shiny? A. Because electrons are ejected from the metal when light shines on it. B. Because photons of light are reflected off the metal. C. Because photons of many wavelengths are absorbed and then re-emitted. D. Because visible light is diffracted by the metal.

Because atoms can move with respect to one another, metals are ...

Malleable and ductile

Because electrons can move around freely, metals ...

Conduct electricity

Band Theory In materials that are insulators (eg diamond), there is a ___________ between the valence and conduction band.

Large energy gap

Band Theory In semi-conductors (eg Si, Ge) there is a _________ between the bands, these materials are often used for solar cells and in computer equipment.

Small gap

Band Theory In metals, the valence band (bonding MO’s) _________ with the conduction band (antibonding MO’s).

Overlaps

Melting to Boiling Do these processes absorb or release energy? A. Absorb B. Release

Melting to Boiling Where does the energy come from? A. The system B. The surroundings

Melting to Boiling Where are the attractions that are being overcome? A. Within particles B. Between particles

Freezing and Condensing Do these processes absorb or release energy? A. Absorb B. Release

Freezing and Condensing Where does the energy go? A. The system B. The surroundings

Freezing and Condensing Where are the attractions that are being formed? A. Within particles B. Between particles

When a substance ______, some of the interactions between the particles must be overcome so that they can move relative to each other.

Melts

When a substance _______, all the interactions between the particles must be overcome.

Boils

The magnitude of the melting point and boiling point provides an estimate of the strength of the __________ between particles.

Attractive interactions

What kinds of interactions must be overcome between particles in order to melt: H2, He, Li, C ? A. LDF B. Covalent C. Metallic D. LDF and Covalent

A, A, C, B

_____________ - Strong (require a lot of energy to break - Caused by attraction of electrons from one atom to nucleus of another atom - Hard to predict bond strength - Present only when atomic orbitals interact constructively - Present within molecules and networks

Covalent bond

______________ - Relatively weak - Caused by fluctuating charge distribution - Increase (predictably) with size of electron cloud - Present between all molecular species

London Dispersion Force

Each carbon atom forms 4 bonds to 4 identical carbon atoms. The bonds arrange them- selves towards the corners of a 4-sided figure. We call this geometry _________.

Tetrahedral

_______________ - Atomic orbitals combine to form an equal number of molecular orbitals. - Each orbital can contain up to two electrons. - Electrons in bonding orbitals stabilize the system. - Electrons in anti-bonding orbital make it less stable. - Electrons are delocalized.

Molecular Orbital

_______________ - Atomic orbitals overlap to form a bond. - The greater the overlap, the stronger the bond. - Each bond made up of two electrons. - Electrons are localized in the bond.

Valence Bond

What is the electron configuration of carbon? A. [He] 2s^2 2p^2 B. [Ne] 2s^2 2p^2 C. 1s2 1p^2 D. [He] 2s^2 4p^2

How many atomic orbitals (on one carbon) must combine to make 4 hybrid orbitals? A. 1 B. 2 C. 3 D. 4

Atomic orbitals “________” (mix up) to form bonding orbitals that then combine with orbitals from other atom to form a bond.

Hybridize

When the hybrid orbitals combine there is a _______ between the bonding and antibonding molecular orbitals.

Large gap

Hybridized atomic orbitals (sp3) overlap to give ...

Strong directed bonds

These bonds are called “sigma bonds”. Sigma bonds form when atomic orbitals overlap ...

End-to-end

Diamond Properties _____________ 3D network of strong bonds, you would have to break bonds to melt.

High mp/bp and/or hard

Diamond Properties _____________ Electrons are localized in bonds between atoms – not free to roam. There is a large “band gap” between the bonding and antibonding orbitals.

Does not conduct electricity

Diamond Properties _____________ Light passes through or is reflected. To absorb light an electron must be promoted to a higher energy level. There is a large “band gap” between the bonding and antibonding orbitals.

Translucent

__________ overlap of atomic orbitals gives π bond.

Side-to-side

The _________ p-orbitals overlap to form pi-bonds. Since the overlap occurs across the entire sheet of atoms, “__________” pi molecular orbitals form over the sheet.

Unhybridized, delocalized

Graphite Properties __________ – because electrons can move freely over the entire sheet within its delocalized pi MOs.

Conducts electricity

Graphite Properties __________ – because it can absorb and emit photons of many wavelengths (just like metals).

Shiny

Graphite Properties _________ – sheets can slide over each other – only “held together” by ...

Slippery, LDFs