Atomic structure

What is the mass of an electron?

1/2000

what was the year John dalton discovered the first thing about the atom and what did he discover?

1803 all atoms are spheres

What was the second thinhg about the atom discovered by J.J Thompson and what was it?

1897 - Plum pudding model

What did Ernest Rutherford discover about the atom and when?

1909 - discovered nucleus, (very small + atom has empty space - electrons negative clouds) - gold leaf experiment

What discovery did Niels Bohr make about the atom and when?

1913 - electrons exist in energy levels (Experiment - EM radiation absorbed, electrons move between shells, energy emitted when electrons move down lower shells)

What was the last discovery about the atom and when?

2000s - subshells

What is the history of the atom?

What do subshells tell us about an atom?

ionisation energies

What is relative atomic mass?

the weighted mean mass of an atom of an element compared to 1/12 the mass of an atom of carbon 12

What is relative isotopic mass?

The mass of an atom of an isotope compared to 1/12 the mass of an atom of carbon 12

what is the equation for relative atomic mass?

What are the molecular ions?

OH^- = hydroxide

NO₃^- = Nitrate

NH₄⁺ = Ammonium

SO₄^2- = Sulfate

CO₃^2- = Carbonate

What is the charge of a zinc ion?

Zn²⁺

What is the experiment for calculating water of crystallisation?

heat hydrated salts until you have a constant mass. = anhydrous salt

How do you calculate water of crystallisation?

1. write out the 2 molecules involved

2. write the masses of each molecule

3. divide these by relative molecular mass to get number of moles

4. divide all the number by the smallest number of moles

Why might % yield not be 100%?

• you may lose product when transfering beaker to beaker

• not all product may have reacted

• products such as gases can escape

• there may be impurities

What is atom economy?

How efficient a reaction is

Why is atom economy important?

• companies try to use reactions that tend towards 100% atom economy

• high atom economies produce less waste = benefit environment

• less by products = less time + money spent separating these form desirable products

• high atom economies mean raw materials used more efficiently = more sustainable

What is a polyprotic acid?

an acid that donates more than one proton

How does ammonia produce OH^- ions?

reacts with water first and accepts a proton to produce ammonium ions (NH₄⁺) and OH^- ions

What happens when ammonia reacts with acids?

What is the colour of phenolphthalein in acids and alkali?

acid - colourless

alkali - pink

What is the colours of methyl orange in acid and alkali?

acid - red

alkali - yellow

neutral - orange

What is a reducing agent?

something which loses electrons but is oxidised itself

What is an oxidising agent?

something which gains electrons and is reduced itself

What is the oxidation number of aluminium?

+3

What is the oxidation number of hydrogen

+1 - except in hydrides - it is -1 (NaH)

What is the oxidation number of chlorine?

-1 except in a compound with F and O - positive value

What is the oxidation number of oxygen?

-2 except in peroxides (-1 H₂O₂) and +2 in OF₂

how many orbitals can the f subshell have and therefore how many electrons can it hold?

7 orbitals so 14 electrons

How many electrons are there in the third subshell?

18

What is the principle quantum number?

the shell number

Do the shells further away form the nucleus have a higher or lower energy level?

higher

Where can the 2 electrons move in the s subshell?

anywhere in the sphere

What does the p subshell look like?

What happens when 2 electrons occupy 1 orbital?

they spin in opposite directions

Are the subshells with the highest energy the most stable?

no they are the least stable

What can you do for a short hand of electron configuration?

put a noble gas in brackets - then add the extra bit

Why do ionic compounds have high melting points?

there are many strong electrostatic forces between oppositely charged ions - lots of energy is needed to overcome these forces

Where is the electrostatic attraction in covalent bonds?

between the shared electrons and the positive nucleus

What is a covalent bond?

the strong electrostatic attraction between the positive nuclei of two non-metal atoms and the shared pair of negative electrons between them

What is a dative covalent bond?

when one atom donates 2 electrons to an atom to form one bond

What is another word for dative bond?

coordinate bond

What are the shape and bonding angles for shapes of molecules with bonding pairs

What is the name and angle of a shape with 5 bonding pairs?

Trigonal bipyramidal (90 and 120) degrees

What is the name and angle of a shape with 6 bonding pairs?

Octahedral (90 degrees)

why is a molecule with 3 bonding regions and 2 lone pairs called trigonal planar?

because one set of lone pairs squash down, and another set push back up so its the same overall angle

What are the names and bond angles of molecules with lone pairs

What is electronegativity?

the ability for an atom to attract electrons towards itself in a covalent bond

where do you go for electronegativity in the periodic table?

the further up and right you go in the periodic table (excluding the noble gases) the more electronegative the element is

The bigger the difference in electronegativity the more …………… the compound

ionic

What is a compound with a difference of 0 in electronegativity?

purely covalent

When can covalent bonds be polar?

if the atoms attached to them have a difference in electronegativty

When do london forces arise?

when molecules are nearby

when we boil a liquid what bonds are we breaking?

the intermolecular forces NOT the covalent bonds

when do permanent dipoles exist?

in molecules with a polarity

What are permanent dipole dipole forces?

weak electrostatic forces that exist between molecules with a polarity e.g. HCl

How can you test for polar molecules?

place a charged rod near a steady stream of polar liquid and it will bend towards the rod as the molecules align to face the oppositely charged rod

Why is ice less dense than water?

it forms a regular lattice structure held by hydrogen bonds and the molecules are further apart - makes ice less dense than water

in terms of bonding what does it mean to have a bigger molecule?

more london forces

are simple molecular molecules soluble in wateR?

depends on their polarity

What is the usual state of giant ionic molecules?

solid

what do polar molecules dissolve in?

polar solvents