Topic 3- Bonding Part 2 Flashcards
What is the definition of electronegativity?
What is the scale called to measure electronegativity?
What is highest on this scale and ignoring what gases?
What are the four most electronegative elements?
Why is nuclear charge a factor affecting electronegativity?
Why is atomic radius a factor affecting electronegativity?
Why is shielding a factor affecting electronegativity (full explanation)?
What aren’t all molecules containing polar bonds?
What is “cancel each other” dipoles?
What is “net dipole” dipoles?
The power of an atom to attract the electrons in a covalent bond to itself
The pauling scale
Fluorine is the highest on the pauling scale (ignoring the noble gases)
Nitrogen, oxygen, fluorine, chlorine
More protons, stronger attraction between nucleus and bonding pair of electrons
Closer to the nucleus, stronger attraction between nucleus and bonding pair of electrons
Fewer shells of electrons between the nucleus and the electrons, less shielding (less repulsion), stronger attraction between molecules and bonding pair of electrons
Not all molecules containing polar bonds are polar overall
If bond dipoles “cancel each other” the molecule isn’t polar
If there is a “net dipole” the molecule will be polar.
What do macromolecular structures have?
How many bonds does diamond have?
What are the four properties of diamond?
How many bonds does graphite have?
What are the five properties of graphite?
What happens to the lone pair of electrons in ammonia?
Why does the diffusion of NH4 OH / HCL reaction happen where it is?
A huge network of covalently bonded atoms
Diamond has four covalent bonds
- Very high melting point
- Very hard
- Will not dissolve in any solvent
- Does not conduct electricity
Graphite has three covalent bonds
- Very high melting point
- Layers “slide” apart
- Low density but strong
- Will not dissolve in any solvent
- Does conduct electricity due to delocalised electrons
Lone pair of electrons have been donated by the N to the H+
Because HCL molecules are smaller and so it diffuses much quicker.
What are intermolecular bonds and not?
What are the three types of intermolecular forces and give them in order of strength from weakest to strongest?
What is an examples of what these forces are responsible for?
What is the bonding like within molecules and between molecules?
What two groups are subject to weak attractive forces?
What two things is the result of electrons moving quickly in orbitals?
What possibility will therefore exist?
What will this then give rise to?
What does the dipole on one atom do?
What are atoms now attracted to each other by?
These are physical, rather than chemical forces
- Van der Waals’ forces (induced dipole-dipole)
- Permanent dipole-dipole forces
- Hydrogen bonding
Melting point etc
Bonding within molecules is strong, that between molecules is weak
Molecules and monatomic noble gases
Their position is constantly changing, at any given instant they could be anywhere in an atom
That one side will have more electrons than the other
A dipole
The dipole on one atom induces dipoles on nearby atoms
A weak force.
What two things does it mean the greater number of electrons?
What do permanent dipole-dipole forces occur between?
What do permanent dipole-dipole forces act in addition to?
What causes more energy must be put into separate molecules?
What happens to the boiling points for these molecules?
What are polar molecules?
What will polar molecules do?
What is hydrogen bonding an extension of?
When and how does hydrogen bonding occur?
What happens as a result of the small sizes of these molecules?
What does this do to the intermolecular attractions?
What does this then lead to?
The stronger the attraction and the greater the energy needed to separate the particles
Molecules containing polar bonds
Basic van der Waals’ forces
The extra attraction between dipoles
Higher boiling points than expected for a given mass
Molecules with permanent dipoles
Attract other molecules with permanent dipoles
Extension of dipole-dipole interaction
Between hydrogen and the three most electronegative elements (Fluorine, Oxygen and Nitrogen- which are extremely polar)
The partial charges are concentrated in a small volume thus leading to a high charge density
Makes the intermolecular attractions greater
Leading to even higher boiling points than expected.
What are the boiling points of hydrides like?
Why must there be an additional molecular force for NH3?
What will each pair of electrons around an atom do?
What do pairs of electrons therefore try to do?
What are the two types of electron pairs and give an example of each type?
What does the shape of molecules depend on?
What fits into a set of standard shapes?
What are all the bond pair- bond pair repulsions?
What must there be when drawing hydrogen bonding?
Not typical of the trend you would expect
NH3 has a higher boiling point than expected for its molecular mass
Will repel all other electron pairs
Try to be as far apart as possible
Shared pair (eg CH4) or a lone pair (eg NH3)
The number of paired electrons around a central atom
Molecules or ions possessing only bond pairs of electrons
All the bond pair- bond pair repulsions are equal
Must have at least two molecules.
What is the bond angle and examples of the following shapes of molecules with lone (unshared) electron pairs:
Linear
Trigonal Planar
Tetrahedral
Trigonal Bipyramid
Octahedral
What is the bond angle and examples of the following shapes of ions with lone (unshared) electron pairs:
Tetrahedral
Triangular pyramid
V-shaped (bent)
Square Planar
180 degree angle, for instance beryllium chloride
120 degree angle, for instance boron trifluoride
109.5 degree angle, for instance methane and ammonium ion
120 and 90 degree angles, for instance phosphorous pentachloride
90 degree angle, for instance octahedral
109.5 degree angle, for instance methane
107 degree angle, for instance ammonia
104.5 degree angle, for instance water
90 degree angle, for instance chlorine tetrafluoride ion.
What happens to the shapes of molecules/ions if they have lone pairs on the central atom?
Why is this?
What two things happen as a result of the extra repulsion?
In what order do the types of repulsion between electron pairs go (from lowest to highest of repulsion increasing)?
What is the definition of metallic bonding?
How do metal atoms achieve stability?
What do these electrons join up to form and what does this prevent?
Why is this?
What are giant structures of metallic bonding called?
What are the positive ions surrounded by in metallic bonding?
What does this mean by delocalised?
The shapes are slightly distorted away from the regular shapes
Because of the extra repulsion caused by the lone pairs
Bond angles tend to be slightly less as the bonds are squeezed together
- Bonding pair- bonding pair
- Lone pair- bonding pair
- Lone pair- lone pair
Metallic bonding involves a lattice of positive ions surrounded by delocalised electrons
By “off-loading” electrons to attain the electronic structure of the nearest noble gas
A mobile cloud which prevents the newly-formed positive ions from flying apart
Due to repulsion between similar charges
Giant Metallic Lattice
A “sea” of delocalised electrons
The electrons are floating around freely, not closely associated with anything else.
How are the atoms arranged in metallic bonding?
What two things does metallic bond strength depend on?
What is the strength of metallic bonding like for the following metals and why:
Sodium
Potassium
Magnesium
What happens the greater the electron density?
What are metals excellent conductors of?
What must a substance have to conduct electricity?
What happens to the electrons because the electron cloud is mobile?
What are electrons attached to the positive end replaced by?
Atoms arrange in regular close packed 3-dimensional crystal lattice
The number of outer electrons donated to the cloud and the size of the metal atom/ion
Relatively weak because each atom donates one electron to the cloud
Weaker than in sodium because the resulting ion is larger and the electron cloud has a bigger volume to cover so is less effective at holding the ions together
Stronger than in sodium because each atom has donated two electrons to the cloud
Holds the ions together more strongly
Metals are excellent conductors of electricity
It must have mobile ions or electrons
The electrons are free to move throughout its structure
Those entering from the negative end.
What does the mobile electron cloud in metallic bonding allow?
What can metals have done to their shapes?
What does malleable mean?
What does ductile mean?
What happens as the metal is beaten into another shape?
What can some metals (such as gold) have happened to them?
What is melting point a measure of?
What is melting point a measure of in metals?
What two factors does the ease of separation of ions depend on in metals?
The conduction of electricity
Metals can have their shapes changed relatively easily
Can be hammered into sheets
Can be drawn into rods and wires
The delocalised electron cloud continues to bind the “ions” together
Can be hammered into sheets thin enough to be translucent
How easy it is to separate individual particles
How strong the electron cloud holds the positive ions
- Electron density of the cloud
- Ionic/atomic size.
What happens to melting point across the period?
Why does the electron cloud density increase?
What happens as a result?
What happens to melting point down the group?
What happens to ionic radius down the group?
What happens as the ions get bigger and so what does this result in?
Melting point increases across the period
Due to the greater number of electrons donated per atom
The ions are held more strongly
Melting point decreases down a group
Ionic radius increases down the group
The electron cloud becomes less effective holding them together so they are easier to separate.
