Bonding Flashcards
How are ionic compounds held together?
Electrostatic attraction between oppositely charged ions
What are ions and how are they removed?
When electrons are transferred from one atom to another
What crystal are giant ionic lattices?
Ionic crystals
Why is if called a ‘giant’ ionic lattice?
It is made up of the same basic unit repeated over and over
What is the electrical conductivity in ionic compounds?
Conduct electricity when they’re molten or dissolved
The ions are free to move then
What is the melting point of ionic compounds?
High melting points - strong electrostatic forces of attraction between oppositely charged ions, taking lots of energy to overcome
What is the solubility of ionic compounds?
Ionic compounds tend to dissolve in water. This is because water is polar and it pulls the ions away from the lattice causing it to dissolve
What are covalent bonds?
Two or more atoms sharing elections to gain a full outer shell. Both nuclei are electrostatically attracted to their sharing electrons
What is the electrical conductivity of simple covalent compounds?
Do not conduct electricity because there are no free ions to carry the charge
What is the melting point of simple covalent compounds?
Low melting points because the weak forces between molecules are easily broken
What are simple covalent compounds?
Strong covalent bonds between molecules but weak forces between molecules
What is the solubility of simple covalent compounds?
Some dissolve depending on how polarised the molecules are
What crystal type are simple covalent compounds?
Molecular crystal
What is another name for giant covalent structures?
Macromolecular structures
Describe the structure of graphite
Arranged in sheets of flat hexagonal carbon atoms. Each carbon is bonded to three others. The fourth outer electron of each carbon is delocalised. Each layer of atoms is held together by weak van der vaals forces
Why is graphite a good lubricant?
Layers can slide over each other due to weak van der vaals forces that are easily broken
What is the melting point of graphite?
High due to the strong covalent bonds
Can graphite conduct electricity?
Yes due to the delocalised electrons that are able to carry an electrical current
Is graphite soluble?
No as the covalent bonds are difficult to break
Why does graphite have a low density?
Layers are quite far apart compared to the length of the covalent bonds
Describe the structure of diamond?
Each carbon is covalently bonded to four others. This means they are arranged in a tetrahedral shape
What is the crystal of giant covalent structures?
Giant covalent?
What is the melting point of diamond and it’s hardness?
Extremely high, and extremely hard. This is because of strong covalent bonds
What is the electrical conductivity of diamond?
Does not conduct electricity. No ions and outer electrons are held in localised bonds
What is the solubility of diamond?
Does not dissolve, strong covalent bonds
Is diamond a good or bad thermal conductor?
Good, vibrations travel easily through the stiff lattice
What is dative covalent bonding?
Also known as co-ordinate bonding, one of the atoms provides both of the shared electrons
How do you identify dative covalent bonding in a molecule?
Identify the atom with the lone pair of electrons, this is the one that provides the bonding electrons
What are charge clouds?
An area where there is a big chance of finding an electron pair
Give two examples of where you will find a charge cloud
In bonding electrons
Lone pairs of electrons
What electron pairs repel the most to least?
Lone pair and lone pair repel the most
Lone pair and bonding pair the second most
Bonding pair and bonding pair the least
What is the bond angle of a molecule that look likes this:
O=S=O. This has one lone pair of electrons
120o
What is electronegativity?
The tendency for atoms to attract bonding electrons towards itself in a covalent bond
What is the most electronegative element?
Fluorine
What is a polar bond?
In a polar bond, the difference in electronegativity between two atoms causes a dipole - slight differences in their charges caused by a shift in electron density in the bond
If the difference between two bonding atoms’ electronegativity is greater, what affect does this have on how polar the bond is?
The greater the difference in electronegativity, the more polar the bond
What is a dipole?
A difference in the charge between two bonding atoms caused by a shift in electron density in the bond
What are intermolecular forces?
Forces between molecules
Name the three types of intermolecular bonding
Van der waals
Dipole-dipole
Hydrogen bonds
How are van der waals forces caused?
These are in all atoms and molecules. At any moment, the electrons are more likely to be on one side than the other. At this point, a temporary dipole is cause. This causes another temporary dipole in an adjacent molecule/atom which are attracted to each other.
Due to the constant movement of electrons, all the dipoles are only temporary
What are permanent dipole-dipole forces?
The positive and negative delta charges cause weak electrostatic forces of attraction between molecules (it’s in HCl)
What is hydrogen bonding?
It only occurs when hydrogen is covalently joined to fluorine oxygen or nitrogen. These are very electronegative so draw the bonding electrons away from the hydrogen atom. The bond is so polarised and as hydrogen has such a high charge density because it’s so small, the hydrogen forms weak bonds with the lone pair of electrons in the F O or N
Put van der waals, hydrogen bonding and dipole-dipole in order from strongest to weakest intermolecular bonds
Hydrogen bonding
Dipole-dipole
Van der waals
What effect do intermolecular forces have on molecules?
Increase melting or boiling point (hydrogen is strong) so require more never to break
Why doe HI have a higher boiling point than HBR?
HI is a larger molecule, with more electrons and therefore will have more dipoles and van der waals forces, requiring more energy to over come
Put these in order of highest to lowest boiling point:
HBR, HI, HF, HCl
HF
HI
HBr
HCl
Describe the structure of metals
Metals exist as giant metallic lattice structures. The outermost shell of electrons of a metal is delocalised. This leaves positive metal ions in a sea of delocalised electrons
What is the bonding in metals?
Positive metal ions attracted to sea of delocalised electrons
What is the melting point of metals?
Amount of delocalised electrons have an effect on the metals boiling point. The more there are, the stronger the metallic bond due to greater electrostatic forces of attraction, the higher the melting point.
How able to be shaped are metals?
Layers of metallic ions can slide over each other meaning they are malleable and ductile
What does malleable mean?
The ability something has to be shaped
What does ductile mean?
The ability for something to be drawn into a wire
What is the electrical conductivity of metals?
Delocalised electrons can carry a charge so they make good electrical conductors
What is the thermal conductivity of metals?
Delocalised electrons can pass kinetic energy to each other, making them good thermal conductors
What is the solubility of metals?
Insoluble accept in liquid metals, due to strength of metallic bonds
Who and when developed the periodic table?
Dmitri Mendeleev, 1800’s
What do the periods show in the periodic table?
Elements within a period have the same number of electron shells
What do the groups in the periodic table show?
Elements in the same group have the same number of electrons in the outer shell so they have similar chemical properties
