The Ozone Story Flashcards
What is electronegativity?
The ability of an atom to attract the bonding electrons in a covalent bond
What is electronegativity measure using?
Pauling Scale
What is the most electronegative element?
Fluorine with a value of 4.0 on the Pauling scale
What happens to electronegativity in periods and groups?
- Increases across periods
- Decreases down groups (ignoring the noble gases)
- Increases as you move towards fluorine
Where do the bonding electrons sit in covalent bonding and when will it be non-polar?
They sit in orbitals between the two nuclei. If they have similar or identical electronegativities, the electrons will sit roughly midway between he nuclei and the bond will be non polar
Are the covalent bonds in homonuclear (diatomic gasses) polar or non-polar and why?
Non-polar because the atoms have equal electronegativities and so electrons are equally attracted to both nuclei
What occurs if the bond between two atoms have different electronegativities?
The bonding electrons will be pulled towards the more electronegative atom, causing the electrons to be spread unevenly so there will be a charge across the bond (each atom will have a partial charge, + or -) and the bond is said o be polar
How can you predict if the bond is polar or non-polar?
If the difference in electronegativity is more than 0.4
What does a molecule rely on to be polar?
The shape and the polarity of the bonds
What is one characteristic of a polar molecule? (dipole)
It had an overall dipole (sometimes referred to as overall polarity) caused by the presence of a permanent charge across the molecule
What occurs in a simple molecule when it comes to electronegativity?
The polar bond gives the whole molecule a permanent dipole and is polar
What occurs in a more complex molecule when all the polar bonds are arranged so they point in opposite directions?
They will cancel each other out and the molecule is non-polar overall
What occurs in a more complex molecule when all bonds point roughly in the same direction?
The molecule will be polar
What are intermolecular bonds?
Forces between molecules that are much weaker than covalent, ionic and metallic bonds.
What are the 3 types of intermolecular bonds?
- Instantaneous dipole- induced dipole bonds
- Permanent dipole- permanent dipole bonds
- Hydrogen bonding (strongest)
What intermolecular bond do all atoms and molecules form?
Instantaneous dipole- induced dipole bonds
How do instantaneous dipoles from?
When the electrons in an atom are more to one side than the other, forming a temporary (or instantaneous dipole).
How do induced dipoles form?
When an instantaneous dipole induces another temporary dipole in the opposite direction on a neighbouring atom
What occurs due to the fact that atoms are constantly moving?
Dipoles are constantly being created and destroyed. Even though the dipoles keep changing, the overall effect is for the atoms to be attracted to one another
What factors of intermolecular bonds affect the intermolecular bonds?
1.The shape
2.How heavy the atom or molecule is (heavier=stronger)
How does the length of a carbon chain effect the strength and why?
The longer the carbon chain, the stronger the id-id bonds because there is more molecular surface contact and more electrons to interact
Why are branched-chain alkanes weaker?
They cant pack as closely together and heir molecular surface contact is smaller meaning fewer id-id bonds can form
Why are heavier/larger molecules stronger?
Because they have larger electron clouds. Molecules with greater surface areas also have stronger id-id forces because they have a bigger exposed electron cloud
What type of intermolecular bonds do polar molecules have?
Permanent dipole- permanent dipole
Why do polar molecules have pd-pd bonds?
The delta + and - charges cause weak electrostatic forces of attraction between molecules. These occur AS WELL AS id-id bonds
When does hydrogen bonding occur?
When hydrogen is covalently bonded to fluorine, nitrogen or oxygen
