Atomic Structure and amount of substance

What was Daltons solid sphere model?

John Dalton suggested that atoms were indivisible solid spheres and suggested that different elements were made up of different types of these spheres

What was Thomson’s plum pudding model 1897?

showed atoms as spheres of positive charge with negative electrons randomly embedded throughout. Showed that atoms are divisible

What was Rutherford’s gold foil experiment ?

In 1909 rutherford fired alpha particles at a sheet of thin gold foil inside a vacuum. They thought the positive would cause slight deflection of all particles. However most alpha particles passed straight through with a few deflecting at large angles. The fact most pass through shows atoms are mostly empty space and those that deflect suggest a dense positive charged nucleus at the atom centre.

What is the nuclear model?

Proposes that the electrons orbit the nucleus in a cloud of positive charge to keep the neutrality of the atom. Henry Mosley shower that the nuclear charge increases by one unit from one element to the next showing that elements vary in proton numbers.

What did James Chadwick discover?

The neutron which made up for why the atomic nuclei was heavier than if there was just protons

What explained why the electrons being attracted to the nucleus wouldnt collapse the atom?

Niels Bohr suggested electrons orbit the nucleus in specific energy levels and can jump between the shells by absorbing or emitting light of particular wavelengths. This later was refined with the introduction of subshells

What are protons and neutrons known as collectively?

Nucleons

What is the relative mass and charge of proton, neutron and electron?

Proton mass 1 and charge +1

Neutron mass 1 and charge 0

Electron mass 0.0005 and charge -1

What is mass number?

The total number of nucleons in the nucleus

What is atomic number ?

The number of protons in the nucleus which uniquely identifies the element

What is an ion?

Atom that have gained or lost electrons resulting in an overall charge

What is an element?

Substances made up of only one type of atom where all the atoms of a substance have the same number of protons

What are isotopes?

Atoms of the same element that have the same number of protons but different numbers of neutrons

What are the chemical properties of isotopes?

Isotopes have the same electron configuration so they have the same chemical properties (reactivity)

What are the physical properties of isotopes?

Isotopes have slightly different physical properties ( mass) because physical properties depend on atomic mass

What is relative isotopic mass?

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

What is relative atomic mass?

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

What is relative molecular mass?

The average mass of a molecule compared to 1/12 the mass of a carbon 12 atom

how to calculate relative atomic mass from isotopic abundances?

(Sum of (isotopic mass x isotopic abundance))/ sum of abundance of all isotopes

What is a mass spectrometer?

An analytical tool used to measure the mass to charge ratio of ions

What happens during ionisation?

Electron impact ionisation= involves bombarding the vaporised sample with high energy electrons to remove an electron from each molecule resulting in +1 ions

Electrospray ionisation= involves dissolving the sample in a volatile solvent and spraying it through a charged needle which adds an H+ ion from the solvent to each molecule

What happens in acceleration?

The positively charged ions are accelerated towards a negatively charged plate by an electric field giving them identical kinetic energy. This means lighter ions will move faster than heavier ones

What happens during ion drift?

The ions enter a flight tube where they drift at a steady speed related to their mass. Lighter ions, having lower m/z ratios, move through the tube quicker and reach the detector sooner than heavier ions

What happens during detection?

As ions hit the detector they gain an electron which creates an electric current. The size of this current is proportional to the abundance of each isotope with more abundant isotopes producing larger currents

What are the number of orbitals and max number of electrons per sub shell?

S=1 orbital max 2 electrons

P-3 max 6

D-5 max 10

F-7 max 14

Why does the 4s sub shell fill before 3d sub shell?

Because the 4s orbital has a lower energy than the 3d orbitals in neutral atoms

Why do electrons in the same orbital have opposite spins?

To minimise electron electron repulsion

What is relative atomic mass?

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

What is relative molecular mass?

The average mass of a molecule compared to 1/12th of the mass of an atom of carbon 12

What is relative formula mass?

The average mass of a formula unit compared to 1/12th of the mass of an atom of carbon 12

How do you calculate number of moles using avogadros constant?

Number of moles= number of particles/ avogadros constant

What assumptions does kinetic theory make about gas particles?

1. Gas particles move rapidly and randomly

2. The volume of the actual gas particles is negligible compared to empty space between them

3. There are no intermolecular attractions or repulsions

4. Collisions between particles are elastic no energy is lost

5. The average kinetic energy of particles depends only on their temperature

What is the ideal gas equation?

pV=nRT

What is the empirical formula?

Gives the simplest whole number ratio of atoms of each element present in a compound

What is the molecular formula?

The actual number and type of atoms of each element in a molecule

What is water of crystallisation?

Water molecules lodged within the lattice framework of an ionic compound

What is anhydrous And hydrated?

An ionic compound without water of crystallisation while one with is hydrated

how do you experimentally determine the formula of a hydrated ionic compound?

1. Heat the hydrated salt to remove water leaving anhydrous salt

2. Calculate moles of water lost and anhydrous salt remaining

3. Find the mole ratio of salt to water

4. Express this ratio in the formula as a whole number

What does atom economy show?

How efficient the chemical reaction is at adding the reactants into the desired product

How do you calculate atom economy?

Mr of desired product/ mr of all reactants x 100

3 environmental and 3 economic reasons why high atom economy is important?

Environmental

1. Less waste is generated reducing disposal impact

2. Raw materials are used more efficiently preserving limited resources

3. Less energy intensive conditions are often required

Economic

1. Reduced costs for separating products from waste

2. Lower raw materials demands decreases expenses

3. Energy costs for heating and pressurising reactions are minimised

What is theoretical yield?

The max mass of product that could be produced from a chemical reaction assuming there is no product loss

3 reasons why the actual yield is always less than the theoretical?

1. Some starting material may not react completely

2. Products can be lost during work up procedures such as filtering or transferring between containers

3. Side reactions may occur reducing the yield of the desired product

What is the calculation for percentage yield?

Actual/ theoretical x 100

What are the 5 compound ions you need to know?

NO3-

CO3 2-

SO4 2-

OH-

NH4 +