Atoms and Fundamental Particles

Fundamental Particles

• Atoms consist of positively charged nuclei surrounded by negatively charged electrons in shells
• The Bohr model can represent the structure of an atom using fundamental particles

Charges and Relative Weights of Fundamental Particles

• Protons have a positive charge
• Neutrons have a neutral charge
• Electrons have a negative charge

Atomic Number

• Indicates the number of protons in the nucleus of an atom
• Identifies an element

Nucleon Number

• Mass number which shows the number of protons and the number of neutrons in the nucleus of an atom

Electron Number

• The number of electrons in an atom or ion
• In a neutral atom, the number of electrons equals number of protons
• In a cation (positively charged ion), the number of electrons is less than number of protons
• In an anion (negatively charged ion), the number of electrons is greater than number of protons

Isotopes

• Particles of the same element that have the same number of protons, but different mass numbers due to different numbers of neutrons

Relative Isotopic Mass

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

Relative Atomic Mass

• RAM is the weighted mean of the atomic masses of the atoms of a particular element relative to 1/12 the mass of carbon-12 atoms
• Chlorine-35 and chlorine-37 occur as isotopes with a 3:1 ratio, making relative atomic mass of chlorine is 35.5
• Bromine-79 and bromine-81 occur as isotopes with a 1:1 ratio, so the RAM of bromine is 80
• Copper-63 has a 69.2% relative abundance and Copper-65 has a 30.8% relative abundance so the relative atomic mass of copper is 63.6
• Magnesium-24 has 79.0%, Magnesium-25 has 10.0%, and Magnesium-26 has 11.0% abundance and the RAM of magnesium is 24.3
• Boron-10 and Boron-11 occur as isotopes with a ratio of 1:4, so the relative atomic mass of Boron is 10.8
• Chromium has four isotopes, Cr-50, Cr-52, Cr-53, and Cr-54, which occur at a ratio of 2:35:4:1, with a RAM of 52
• Gallium-69 and Gallium-71, the RAM of gallium is 69.7 and the relative abundance of each isotope is 0.65 : 0.35
• Potassium-39 and potassium-41, find the RAM of potassium is 39.1 and the relative abundance is 0.95 : 0.05

Isotopes as Tracers

• Oxygen has two isotopes, oxygen-16, the most common isotope, and oxygen-18
• Carboxylic acid can be produced to contain only oxygen-16 and alcohol produced to contain only oxygen-18
• Carboxylic acid and alcohol react using an H+ catalyst
• Products are collected where their Relative Molecular Mass is measured using mass spectroscopy
• Products include ethyl ethanoate (RMM of 90) and water (RMM of 18)
• Oxygen-18 from the alcohol becomes part of the ester
• Alcohol loses a hydrogen as the O-H bond breaks
• Carboxylic acid loses an OH as the C-O bond breaks
• The H and OH lost will form water, while an ester is produced

Radioactivity

• Radioactive decay involves nuclei losing energy by emitting radiation in the form of alpha particles, beta particles and gamma rays
• Unstable nuclei become more stable during this process

Alpha Particles

• Composed of a helium nucleus made of two protons and two neutrons

Beta Particles

• Composed of high-speed electrons

Gamma Rays

• High energy electromagnetic waves

Properties of Particles and Rays

• Alpha particles deflect towards negative charges, have low penetration power
• Beta particles deflect towards positive charges, have medium penetration power, stopped by aluminum
• Gamma rays have no interaction and high penetration power, stopped by lead/concrete

Half-Life

• The time taken for half of the atomic nuclei in a radioactive sample to decay
• Half-life of iodine-123 if 12.5% of the original quantity remains after 39.6 hours is 13.2 hours
• A radioactive isotope sample producing 210.0 counts per minute shows 52.5 counts/minute after 28 days; its half-life is 14 days.
• 280 mg of francium-223 takes 66 minutes to reduce to 35 mg, thus its half-life 22 minutes
• Decay of 180g of Cs-137 to 22.5g, with a half-life of 30 years, would take 90 years
• A rock sample 3.9-million-year-old rock, contains 4.5 mg of rock and 1.3 is the half life, thus the rock would contain 36mg per kg of rock.
• Half-life of Calcium-47 is 4.5 days, and will contain 25mg of calcium after 13.5 days
• Starting with 80 mg of tritium with a half-life of 12.3 years, there will be 10mg left after 36.9 years
• Fermium-253’s half-life is 3 days and 25% would remain after 6 days
• Half-life of iodine-131 is 8 days
• Remaining mass and percentage of iodine-131 after 16 days is 11g or 25% total

Carbon Dating

• Carbon naturally occurs in isotopes carbon-12, carbon-13, and carbon-14
• Carbon-14 is radioactive, decays by emitting a beta-particle, and has a half-life of 5730 years
• A piece of wood with 25% of its original carbon-14 content is 11,460 years old
• A prehistoric man was found to have lived 11,500 years ago and had 25% of the original carbon
• Ice containing 12.5% carbon-14 formed 17,190 years ago given the half-life of carbon-14 at 5730 years
• Archaeologists found pottery contains organic material, from which 75% as been dropped, thus pottery would be around 11,460 years

Nuclear Equation

• Nuclear equations must have conserved mass and charge numbers
• Magnesium-26 bombardment equations are: Mg + n→ β + Al
• Uranium-235 bombardment equations are: U + n →3 n + Ba + Kr
• Aluminium-27 bombardment equations are: Al + α→ P + n
• Nitrogen-14 bombardment equations are: N + α→ H or p + O
• Thorium-228 decay equations are: Th → α + Ra
• Cesium-137 decay equations are: Cs → β + Ba
• Carbon-14 decay equations are: C → N + _° β
• Uranium-235 reaction equations are: U + n→ Kr + Ba + 2 n
• Uranium-235 + neutron → Lanthanum + Bromine + 3 neutrons: U + n→ La + Br + 3 n
• Plutonium + alpha → Curium + neutron: Pu + α → Cm + n
• Uranium-235 + neutron → Cesium + Yttrium + 2 neutrons: U + n→ Cs + Y + 2n (Note: these may be isotopes)

Quantised Energy Levels in Atoms

• Shells are numbered 1, 2, 3, and so on
• Subshells include s, p, d, f

Subshells

• The s subshell can hold a max of 2 electrons
• The p subshell can hold a max of 6 electrons
• The d subshell can hold a max of 10 electrons
• The f subshell can hold a max of 14 electrons

Orbitals

• Each orbital can hold a maximum of two electrons, with opposite spins
• The s-subshell has one spherical orbital
• The p-subshell has 3 dumbbell-shaped orbitals that occur at 90° to each other
• The d-subshell has 5 orbitals
• The f-subshell has 7 orbitals

Atomic Energy Levels and the Aufbau Principle

• Electrons fill lower energy orbitals first (1s, then 2s, etc.)
• A maximum of two electrons can occupy an orbital
• If there are multiple orbitals at the same energy level, electrons first fill orbitals as unpaired before pairing up

Order of Filling Electrons

• 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s
• Electrons are added using the Aufbau principle
• Electronic configuration is written with shell numbers
• Electronic configurations for H to Kr must be constructed using spdf notation and electrons-in-boxes

Atomic Orbitals

• S and P orbitals are to be sketched from previous notes
• Shapes and hybridised Orbitals sketched are sp, sp2, and sp3
• Hybridisation between hybridised Carbon Atoms are in O. Chem.
• Relationship between hybridised molecular geometry is covered

Ionisation Energy

• The process of losing electrons
• Explain the 1st ionisation as it varies as you move through the second and third segment
• Explaining general trends and other inconsistencies that may occur
• Explaining all trends as being up or down a segment in the period table

Ionisation: energy

• Electrons are associated with loss
• The required energy is known as endothermic, for 1 mol gas this leads from losing 1 mole Electrons this leads from positive ions
• The Ionization element is the first element known as x
• In an another case it is required that the energy and the outmost energy from the given mole turns into to being gassy, the ions will then turn into +2

Equations:

• In order to ionise you need to right equations properly
• Need to write first ionisation
• The most imporatnt equation is the equation for Sodium:

Ionisation Sodium

• In Sodium the same rules apply as the main subject, a number of rules that have to be followed

Influences to Ionisation energy

• The strongest amount of attraction happens to be the nucleus of the atom and its outer electron (when the nucleaus becomes bigger, leads to more and more energy
• The atomic size and distance needs to be bigger to measure the the electron size and energy
• When it comes is to shield/ screens the energy is in the form of an inner and outer shell
• Changing from s to p -orbitals has is related to a shield

Comparison of the first ionisation from Helium to to Hydrogen:

• What ever you do make sure you are consitent with the equations and data

Successive Ionisation energies of an element

• By not directly following the syllabus there is more than enouhg succesive ionisation that can lead to a atoms size
• The ammount of atoms needs to be the same to know how to ionise from a given atom. For instance Carbon needs six electrons to ammount to its lose

Each must fall under such requirements

• Carbon

• Electron

• Ion

• Each and every pattern the the need form electron

• Its endothermic that requires all energy (the more and more electrons all of them becomes deiffcult its more outter to electron)

• As a whole its its empties from a shell, each has to be be removed for the ammount of shell

• Electronegativity*

• Explains why this is endothermic and the sub-equent affection that needs to be there

The effect is by

• How effective a charged atom
• An affect is by the charged ion of 1 degree or less for an electron
• Must compare all if the same