Chemical Bonding and Structure Flashcards
Multiple covalent bonds are caused by what?
Strong electrostatic forces of attraction between the nuclei and shared electrons
Lone pairs of electrons can affect what about the molecule?
It’s shape.
Lone pairs of electrons can form what with other atoms?
Dative covalent bonds (coordinate bonds).
A sigma bond is what?
A sigma bond is your basic head-on covalent bond with the bond in line with the bonding orbitals.
How many sigma bonds can you only ever have between any two atoms?
One.
A pi bond is what?
A pi bond is a covalent bond between orbitals perpendicular to the bond direction. This is usually p-orbitals, never s.
Electron pairs do what to each other?
Repel each other, as they are negatively charged.
Molecules are shaped so that what can be said to be true?
Molecules are shaped so that electron pairs are arranged to be as far away from each other as possible.
2e pairs makes what shape and what bond angle?
Linear, 180 degrees.
3e pairs are arranged in why shape with what bond angle?
Trigonal planar, 120 degrees.
4e pairs makes what shape with what bond angle?
Tetrahedral, 109.5 degrees.
Electron pair repulsion theory is the theory that…
…a lone pair exerts more repulsion than a bonded pair. This is about 2.5 degrees per lone pair and examples of these are water and ammonia bond angles (104.5 and 107).
Double and triple bonds act as what when we consider molecule shapes?
They act as a centre of negative charge causing similar shapes to molecules with singly bonded electron pairs.
If the two atoms covalently bonded are the same what can be said about the electrons?
They are shared equally between the two atoms.
What is a polar covalent bond?
When two atoms are covalently bonded but one atom has a nucleus that the electrons are more attracted too.
What happens to a atoms of they have a polar covalent bond between them?
Dipoles form with a delta negative where the electrons are closer too and a delta positive where the electrons are further from. Overall there is no charge as these charges are equal and cancel.
What is electronegativity?
Electronegativity is the ability of an atom to attract the bonding electrons in a covalent pair.
How can electronegativity be used to predict the extent to which the bonds between different atoms can be polar?
The greater the difference of the electronegativity of the atoms bonding, the greater the polarity of the covalent bond between them.
Electronegativity does what across a period?
Increases.
Why does electronegativity increase across a period?
The nuclear charge increases but the number of shielding electrons remains constant, so the attraction for the shared electrons pairs increases.
What type of diffraction can be used for chemists to work out structure?
X-ray diffraction.
Microwave spectroscopy can give chemists information about what?
Bond lengths between atoms.
Bond length depends on what?
Size of atom. Single bonds are longer than multiple bonds as there are less electrons in the shared electron cloud.
Sigma bonds are how strong relative to pi bonds?
Sigma bonds are far stronger as they are closer to the nucleus and experience stronger attraction, therefore are more difficult to break.
