PFAHS +
Electronegativity
Electronegativity
Electronegativity
Bond Dipole Movement
Atomic Radius & Bond Length
Bond Enthalpy
100
What are PFAS?
PFAS are synthetic chemicals used for water and grease resistance in products like non-stick cookware, clothing, and food packaging. They persist in the environment and can harm health, leading to growing concerns and regulations
100
How does Electronegativy apply to PFAS?
The electronegativity difference between carbon and fluorine atoms in a C-F Bond causes the fluorine atom to have a partial negative charge (δ-) and the carbon atom to have a partial positive charge (δ+). This polarity is crucial to the properties of PFAS.
100
Address Dipole moment bond using Electron Density, where electrons spend more time, and how this impacts the C-F bond vs C-I bond.
The C-F Bond has a strong Dipole moment because electrons spend more time near fluorine, creating a strong δ+ on C & δ- on F. This leads to high bond stability & environmental persistence. Unlike C-l which has a weaker Dipole moment, meaning less polarity, weaker bonding, & faster degradation.
100
What does the Atomic Radius and Bond Length mean?
The atomic radius is the size of an atom, influencing how it interacts in bonds. The bond length is the distance between bonded nuclei, determining bond strength. The smaller atomic radius + higher EN = shorter, stronger bonds (C-F). While a larger atomic radius + lower EN = longer, weaker bonds (C-l).
100
What does Bond Enthalpy measure?
Bond enthalpy measures the energy needed to break a bond.
Higher bond enthalpy = stronger, more stable bond (C-F)
Lower bond enthalpy = weaker, more reactive bond (c-l)
200
Describe what an image of the skeletal structures of PFAS looks like?
200
What is the electronegativity of C, F, I, and Electronegativity Difference between C-F and C-I?
The electronegativity of C is approximately 2.55, F is approximately 3.98, and l is approximately 2.66. The electronegativity difference between C-F is 3.98-2.55=1.42, and between C-l is 2.66-2.55=0.11.
200
What are dipole arrows?
Points from positive to negative charge
200
How does atomic radius and bond length affect each trend on the PT?
The atomic radius increases down a group and decreases across a period. Bond length follows a similar trend. Bond strength and bond length have an inverse relationship; shorter bonds are stronger.
200
How do the C - F and C - I bonds compare with regard to Bond Enthalpy?
C-F bond is much stronger than C-l bond due to shorter bond length, higher electronegativity difference, and better orbital overlap.
C-F is highly resistant to breaking, which explains why PFAS persist in the environment, while C-l breaks more easily and degrades faster.
300
What are PFAS substances?
PFAS are Per- and polyfluoroalk substances that are synthetic chemicals used for their water, grease, and heat-resistant properties.
300
How does electronegativity impact bond type and what does it create?
Electronegativity differences determine bond type: small difference = nonpolar covalent, very large difference = ionic.
300
Fill in the blank: More electronegativity difference means a_____
stronger dipole
300
What is the relationship between bond strength and bond length?
Shorter bonds = stronger bonds (C-F)
longer bonds = Weaker bonds (C-l)
300
How does B.E. impact the PFAS molecule?
The high bond enthalpy of the C-F Bond in PFAS directly impacts the stability, environmental persistence, and toxicity of these molecules. Strong C-F bonds resist degradation, leading to their accumulation in both the environment and living organisms, making PFAS particularly problematic for long-term environmental and health concerns.
400
Where are PFAS found? (list at least 8 different uses)
Link to photos that may help: https://docs.google.com/presentation/d/1ajj562vxZL-Y3CXFOAMhe2FVff45sx15lFyKwR1c5yc/edit?usp=sharing
They can be found:
Non-stick cookware
Water-resistant fabrics
Grease-resistant paper
Building materials
Electronics
firefighting foams
cleaning products
medical products
400
Why is a C - F more problematic than a C - I?
C-F is more problematic that C-l because of fluorine's much higher electronegativity, creating a highly polar and reactive bond.
400
Fill in the blanks: Symmetric molecules can have dipoles that ___ ____.
cancel out
400
Cations are ____ than their neutral atoms
smaller
400
Fill in the blank: When you form a bond ___ is released.
energy
500
PFAS can build up in the body, leading to what concerns?
Health concerns
500
What is the most electronegative element?
Fluorine
500
What do polar bonds create?
Polar bonds create dipole movements in a molecule
500
Fill in the blanks: Higher nuclear charge pulls electrons closer, reducing ___
atomic size
500
Fill in the blank: When bonding enthalpy it is how much energy you need to break a bond between ___.
atoms