Unified atomic mass unit connects to our units of mass that we may use on a larger scale.

defined this way because it makes it a lot cleaner when we think about whether it is the mass of an atom or the mass of the subatomic particles of an atom such as a proton

Mass of hydrogen would be mass of a proton + mass of an electron. Will be roughly the mass of one proton. Weighted average

Mass of an element on the periodic table - known as the average atomic mass

Calculate the number of moles in a 1.52 kg sample of Glucose (C6H12O6)

mass = moles* mr moles = mass/ mr and mr = mass/moles

Molar mass of C - 12.01 g/mol Molar mass of H - 1.008 g/mol Molar mass of O - 16.00 g /mol

(6 x Molar mass of C) + (12 x Molar mass of H) + (6 x Molar mass of O)

Isotope - a form of an element that has a different number of neutrons but the same number of protons to that of another of the same element.

The mass of chlorine shown on the periodic table is an average of 75.77% of Cl 35 and the 24.24% of the Cl 37

Relative atomic mass = sum of (abundance x mass) / 100

Sample enters one end, and is beamed by electrons (which can knock of electrons from the sample and can ionise them)

Now that they now have been ionised they can now be accelerated through electric plates and they move rapidly through the chamber where they then enter a magnetic field

A strong magnetic field can bend the path, can deflect the ions with charge

For a given charge, the force of deflection will be the same. But if you have a larger mass, you will be deflected less. Lower mass - deflected more

The different isotopes are being deflected different amounts as they go through the magnetic field.

Then there is the detector. At different points of the detector each of the isotopes will be detected.

The more ions that hit a certain part of the detector, means that you have more of that isotope

Atoms that have the same number of protons but different numbers of neutrons are known as isotopes.

The relative abundance of an isotope is the percentage of atoms with a specific atomic mass found in a naturally occurring sample of an element.

The average atomic mass of an element is a weighted average calculated by multiplying the relative abundances of the element's isotopes by their atomic masses and then summing the products.

The relative abundance of each isotope can be determined using mass spectrometry.

A mass spectrometer ionizes atoms and molecules with a high-energy electron beam and then deflects the ions through a magnetic field based on their mass-to-charge ratios (m/zm/zm, slash, z).

The mass spectrum of a sample shows the relative abundances of the ions on the y-axis and their m/zm/zm, slash, z ratios on the x-axis. If z = 1z=1z, equals, 1 for all ions, then the x-axis can instead be expressed in units of atomic mass (\text{u}ustart text, u, end text).

Different ways to represent a molecule: by name (e.g. Benzene, empirical formula (gives you a ratio of the elements in the molecule e.g. CH), the molecular formula (C6H6) and the structural formula (gives you the structure or start to give you the structure of the molecule.

E.g. Molecular formula for glucose (C6H12O6) (C- 12.01 u, H - 1.008 u and O - 16.00 u)

Can you figure out the percentage of Carbon by mass of a sample of glucose based on the molecular formula?

mass of 6 moles of carbon / the mass of 1 mole of glucose is equal to (6 moles of Carbon x the molar mass of carbon) / (mass of 6 moles of carbon + mass of 12 moles of hydrogen + mass of 6 moles of oxygen

E.g. a molecule in a container is 73% by mass mercury and by mass it is 27% chlorine.

What is the ratio between the number of moles that we have of mercury and the number of moles that we have of chlorine

Assuming that the entire container is 100g, we have 73g of mercury and 27g of chlorine

So we would do 73 g x (1/200.59 moles per gram) = roughly 0.36 moles

For chlorine we would do 27 g x (1/35.45 moles per gram) = roughly 0.76 moles

We have roughly 2 times the amount of chlorine atoms than mercury atoms so the empirical formula would most likely be HgCl2

Coulomb's law can be viewed as saying that the magnitude of force between two charged particles is going to be proportional to the charge on the first particle times the charge on the second particle divided by the distance between the two particles squared

q1 can be viewed as the effective positive charge from the protons and q2 can be viewed as the charge of an electron

The distance between the two charges is going to be the distance between the nucleus and the electrons on the outermost shell or the valence electrons

We can view this effective charge as being equal to the distance between the charge in the nucleus (the atomic number) and the difference between that and S (how much shielding there is (approximated by the number of core electrons

Effective charge increases as you go from left to right on the periodic table

As you go from left to right on the periodic table the radius decrease

The first ionization energy is the minimum energy required to remove that first electron from a neutral version of that element.

Ionization energy will be high in cases of when the coulomb forces are high

Low radius and the effective charge make the coulomb forces high

As you go left to right on the periodic table the effective charge increases

Electron affinity - how much energy is released if we add an electron

Ionization energy - the energy it takes to remove an electron

High electron affinities in the top right of the periodic table. Low electron affinities at the bottom left

The convention is that when you release energy you have a negative electron affinity

Electron negativity - when an atom shares a pair of electrons with another atom, how likely is it to attract that pair to itself vs for the pair to be attracted away from it to the other one

Atomic radius - half of the distance between the nuclei of two bonded atoms

As you go down a group the atomic radius increases because you are adding electrons in higher energy levels that are farther away

As you go across a period (row) from left to right the atomic radius decreases

Electronic shielding the blocking of valence shell electron attraction by the nucleus, due to the presence of inner-shell electrons.

The more positive charge the more attraction between the nucleus and the outermost electron

As you go across the row (left to right) atomic number increases meaning that the increased pole will pull the electrons in closer, decreasing the size of the atom

When Li loses an electron it loses the outermost electron and as a result it has 3 positive charges in the nucleus but only 2 electrons

Noble gas configuration for the neutral chlorine: noble gas 3s^2 3p^5

Noble gas configuration for the chlorine anion: [Ne] 3s^2 3p^6 - 8 electrons in the outer shell

Ionization energy - the energy required to move an electron from 1 mole of gaseous to produce 1 mole of gaseous ions

A represents a neutral atom, the positively charged nucleus attracts the electrons, it will take energy to pull an electron away from that attractive force of the nucleus

Ionization energy: H = +1312, Li = +520, Na = +496, K = +419

As you go down the group there is a decrease in ionization energy

Nuclear Charge: the more positive charges you have, the more of an attractive force the electron would feel -. therefore harder to pull the electron away. Increase the nuclear charge, increase the ionization energy

Electron Shielding - the blocking of valence shell electron attraction by the nucleus, due to the presence of inner-shell electrons. Decreases ionization energy

Effective nuclear charge (Zeff) = nuclear charge (Z) - the effect of the shielding electrons (S)

Distance of the outer electron fro the nucleus: the closer it is the more of an attractive force it has for the nucleus. Decrease in ionization

Leucippus and Democritus - came up with the idea that matter is composed of tiny particles. They gave these particles the name 'A tomos' meaning uncuttable or indivisible. They thought that ions atoms were hard and stuck together with hooks. Clay atoms were softer and attached by ball socket joints, making them flexible.

Antoine Lavoisier - proposed the Law of the Conservation of Mass

In the 1870s scientists began probing stuff was made of using discharge tubes (gas filled tubes with electrodes at each then which emit light when an electric current passes through them.

1886: German physicist Eugen Goldstein found that the tubes also emitted light from the positive electrode, meaning that there must also be a positive charge in matter .

J J Thompson measured how much heat the cathode rays generated, how much they could be bent by magnets and other things, and was able to measure the mass of the rays

The mass was a thousand times lighter than a Hydrogen atom

Concluded that the cathode rays were not rays or waves but were very light, very small negatively charged particles - named corpuscles, we call them electrons

Thompson thought that the electrons were randomly distributed in a positively charged matrix - The Plum Pudding model.

Ernest Rutherford in 1909 did his gold foil experiment. He surmised that that the tiny positively charged ions were fundamental particles - protons

Heisenberg discovered that it is impossible to know with certainty both the momentum of an electron or any subatomic particle and its exact position

Quantum style electrons are mostly drawn as clouds with the intensity of colour representing not individual electrons but the probability of finding one. Quantum model is often called the Cloud model of the atom

J.J. Thomson's experiments with cathode ray tubes showed that all atoms contain tiny negatively charged subatomic particles or electrons.

Thomson's plum pudding model of the atom had negatively-charged electrons embedded within a positively-charged "soup."

Rutherford's gold foil experiment showed that the atom is mostly empty space with a tiny, dense, positively-charged nucleus.

Based on these results, Rutherford proposed the nuclear model of the atom.

In 1911, Bohr came to realise that the mathematical principles could be applied to Rutherford's model. His analysis of the gold foil experiment, allowed him to predict the most likely positions of electrons within the atom. Bohr's resulting model, sometimes called the Planetary model represents the electrons in orbits around a small central nucleus. Each orbit can have a specific number of electrons which correlates to the energy levels and orbitals in the modern model of the atom

As you go left to right on the periodic table the effective charge increases

Effective nuclear charge (Zeff) = nuclear charge (Z) - the effect of the shielding electrons (S)

The ionization energy of the elements within a period generally increases from left to right. This is due to valence shell stability. The ionization energy of the elements within a group generally decreases from top to bottom. This is due to electron shielding.