Intermediate Bonding, Polarity, Intermolecular Forces and Solubility Flashcards
What does electronegativity measure?
The ability of an atom to attract an electron pair to itself in a covalent bond.
What is caused if the difference between electronegativity of atoms in a molecule are high?
A dipole
What does the bond polarity of a compound tell us?
The reactivity of a particular compound
What are intermolecular forces?
The forces between MOLECULES
What are the three main types of intermolecular forces?
- London forces
- Permanent dipole-dipole
- Hydrogen bonds
What are London forces caused by?
Instantaneous electron distribution in an atom, which results in a temporary dipole
What does a temporary dipole cause?
An induced dipole in the opposite direction on a neighbouring atom
What does the instantaneous electron distribution in an atom result in?
Weak attractive forces
What results in greater London forces?
More electrons, which result in a greater induced dipole, which results in larger London forces
What are permanent dipole-dipole forces caused by?
Difference in electronegativity
What is Hydrogen bonding?
The attraction between Hydrogen in a polar bond and non-bonding electron on a nearby small electronegative ion
What are the three atoms that H can bond to that will result in Hydrogen bonding?
Fluorine, Oxygen, Nitrogen (FON)
How strong is Hydrogen bonding in comparison to London forces?
Hydrogen bonding results in a greater attraction between atoms in comparison to London forces.
Why does boiling temperature increase as an alkane chain length increases?
The molecules are larger, so the London forces are greater
Why are London forces greater in a straight chain, than they would be in a branched chain?
- Chains can line up
- Larger surface area
- Force is maximised
Why do alcohols have higher boiling points than alkanes with the same number of electrons?
The H-O bond allows them to form Hydrogen bonds
Why is fluorine an exception to the idea of increasing boiling points going down the halide group?
- Fluorine has fewest electrons
- But has much higher boiling point
- Able to form Hydrogen bonds (FON)
Under what condition does a solution form?
A solution forms when one substance is dispersed uniformly throughout another
Which points should you mention when comparing the solubility of liquids?
- The intermolecular forces of EACH liquid
2. New potential intermolecular forces forming between 2 substances
Why might two liquids not mix together?
- One may have stronger forces of attraction than the other
- Energy given out when new attraction forms is not sufficient to overcome the energy required to break the existing forces
The energy required to overcome strong electrostatic forces of attractions in an ionic lattice is supplied by what?
The energy released when polar water molecules are attracted to the ions
What is meant by the term ‘hydration energy’?
The energy released when ions are hydrated due to them being surrounded by water molecules
What are the characteristics of the more electronegative elements?
Higher nuclear charges as there are more protons in the nucleus and similar atomic radii
What is the pattern for increasing electronegativity in terms of the periodic table?
Across the periods and up the groups
