Topic 2 Bonding and structure Flashcards

Question

What are the features of metals?

Answer 1

Metals are good thermal conductors as the delocalised electrons can transfer kinetic energy Metals have high MP due to the strong electrostatic attractions Solid metals are insoluble as the metallic bond is too strong to break Metals are malleable and ductile as the ion layers can slide when hit with a hammer and still retain an attraction between ions and delocalised electrons Metals are good electrical conductors as the delocalised electrons are mobile and can carry a current

Answer 2

Electronegativity is the ability of an atom to attract electrons toward itself in a covalent bond The further up and right you go, the more EN the element is. Fluorine is the most EN The bigger the difference in EN, the more ionic the compound will be. A difference of zero will be purely covalent

Answer 3

Covalent bonds can become polar if the atoms attached to it have a difference in EN The bigger the difference in EN, the more polar the bond will be. Cl is more EN than H so it is the more electronegative element To show a polarity we use a delta - and delta + Atoms that are bonded with the same or similar EN values aren't polar. Look out for whole molecules that may appear to be polar. If the polar bonds are arranged symmetrically then you have no overall polarity

Answer 4

Hydrogen bonding permanent dipole - dipole London (instantaneous) Gets weaker as you go down

Answer 5

Any molecule or atom with electrons can form a dipole when it moves near another atom or molecule This occurs as electrons in a molecule or atom can move from one end to another. Hence creating a temporary dipole This temporary dipole only exists when 2 molecules or atoms are nearby. When they move away the dipole interaction is destroyed The delta+ atom on one atom or molecule will be attracted to the delta- on another and a force of attraction is created

Answer 6

London forces can hold some molecules in crystal structures The bigger the molecule or atom, the more London forces as you have larger electron clouds When we boil a liquid, we are breaking the weak London forces NOT covalent bonds Longer straighter chain hydrocarbons have more London forces and so more energy is needed to overcome them. This means the BP increases Hydrocarbons with branches means that they can't pack together as close. This weakens the London forces between the chains and lowers their BP

Answer 7

There are wea electrostatic forces that exist between molecules with a polarity. The delta - part on one molecule is attracted to the delta + on another. Unlike London forces, dipole-dipole interactions involve molecules with a permanent dipole and so are stronger. Molecules that have dipole-dipole interactions also have London too

Answer 8

Polar molecules (like water) can be tested by placing a charged rod near a steady stream of polar liquid. You should see the liquid bend towards the rod as the molecules align to face the oppositely charged rod

Answer 9

This is the strongest IMF and occurs only when you have very EN elements. It occurs when Hydrogen on one molecule forms a bond with the lone pair of oxygen, nitrogen or fluorine. You can show hydrogen bonding using dotted lines between lone pairs and hydrogen Molecules that have hydrogen bonding also have London and Dipole-Dipole too

Answer 10

Ice forms a regular structure held by Hydrogen Bonding. The orientation of hydrogen bonds pushes the molecules further apart. This makes ice less dense than water. Alcohols are not as volatile as alkanes with similar masses due to hydrogen bonding. Alkanes have weaker London forces. HF has a higher BP than HCL as it has hydrogen bonding. More energy is needed to overcome the electrostatic forces There is a slight increase in BP from HCL due to the increased mass of molecule, hence a bigger electron cloud and more London Forces.

Answer 11

Solvent bonds must break Substance bonds must break New bonds should form between the solvent and the substance

Answer 12

Polar substances can dissolve in polar solvents These are molecules that have a polarity. Some hydrogen bonds. Some have permanent dipole-dipole interactions and London forces Most ionic compounds dissolve in polar solvents like H2O. The delta H+ is attracted to the negative ions and the delta - oxygen is attracted to the positive ions. The water molecules surround the ion in a process called hydration For this to happen, the new bonds formed must be the same strength or greater than those broken. If not then the substance is very unlikely to dissolve Some non-ionic substances can dissolve too. Alcohols dissolve in polar solvents as they can hydrogen bond with water molecules. The hydrocarbon part is non - polar so it doesn't dissolve in water. The bigger the hydrocarbon part, the less soluble the alcohol is. Some polar molecules don't dissolve in water. Haloalkanes don't dissolve as their dipoles aren't very strong. Water forms stronger hydrogen bonds between each other rather than with haloalkanes so haloalkanes are insoluble. They can dissolve in solvents that interact via permanent-permanent dipole interactions though.

Answer 13

Non-polar substances can dissolve best in non-polar solvents. These are molecules that don't have a polarity. An example would be alkanes as they only have London forces Non-polar molecules tend not to dissolve well in water as water forms stronger hydrogen bonds between each other rather than interacting with non-polar molecules