Atomic Structure
- Created by: Megan Lewsley
- Created on: 28-04-17 22:49
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- Atomic Structure
- The Atom
- Mass & Atomic Number
- Neutral atoms, number of electrons = number of protons.
- Neutrons = mass no - atomic no
- Atomic Number - Protons only in nucleus. Identifies element.
- Ions = atoms with gained or lost electrons. Negative charge = gained. Positive = lost.
- Isotopes have same chemical but different physical properties. E.g. Different densities and rates of diffusion because they depend more on mass of atom.
- Mass Number - Total number of protons & neutrons in nucleus
- Neutral atoms, number of electrons = number of protons.
- Structure of Atom
- Elements made from atoms. Atoms made from protons, neutrons & electrons
- Protons & neutrons in nucleus. Electrons in orbitals.
- Elements made from atoms. Atoms made from protons, neutrons & electrons
- Isotopes
- Mass & Atomic Number
- Relative Mass
- Calculating Relative Atomic Mass
- (Isotopic Masses x percentages) / 100 (total percentage)
- Relative Isotopic Mass
- Mass of atom of isotope on scale where carbon 12 = 12.
- Relative Molecular Mass
- Mr = Average mass of a molecule on a scale where carbon 12 = 12
- Mr = add up Ar of all atoms in molecule
- Relative Atomic Mass
- Ar = average mass of atom on scale, carbon 12 = 12.
- Relative Formula Mass
- Average mass of a formula unit on scale where carbon 12 = 12
- Used for ionic compounds. Add Ar of all molecules taking ions into account.
- Average mass of a formula unit on scale where carbon 12 = 12
- Calculating Relative Atomic Mass
- Mass Spectrometer
- How it Works
- 1. Electrospray Ionisation - Dissolved in polar substance, pushed through nozzle at high pressure. High voltage applied, loses electron, separated from solvent.
- 2. Acceleration - Positive ions accelerated by electric field. Same kinetic energy to all ions. Lighter ions accelerate more.
- 3. Ion Drift - Ions leave electric field with constant acceleration & KE. Enter region of no electric field with same acceleration. Lighter ions travel faster.
- 4. Detection - Lighter ions travel faster, reach the detector in less time. Detects the current created when hitting the detector. times how long in the spectrometer for. Calculates mass / charge values to produce mass spectrum.
- 3. Ion Drift - Ions leave electric field with constant acceleration & KE. Enter region of no electric field with same acceleration. Lighter ions travel faster.
- 2. Acceleration - Positive ions accelerated by electric field. Same kinetic energy to all ions. Lighter ions accelerate more.
- 1. Electrospray Ionisation - Dissolved in polar substance, pushed through nozzle at high pressure. High voltage applied, loses electron, separated from solvent.
- Interpreting a Mass Spectrum
- Data from spectrometer.
- If sample is an element, each line is an isotope. Y-axis is the abundance of ions. X-axis is mass/charge ratio. All are ions (1+) presume it is the relative isotopic mass. Height of peaks is relative isotopic abundance.
- Data from spectrometer.
- Identifying Element
- Elements with isotopes has more than one line, produces characteristic patterns used to identify a certain element.
- How it Works
- Using Mass Spectra
- Calculating Relative Molecular Mass
- Mass/charge ratio = Mr, used to identify an element.
- Calculating Relative Atomic Mass
- 1. Read % abundance from y-axis & Relative isotopic mass from x-axis. Multiply = total relative mass for each isotope.
- 2. Add up totals.
- 3. Divide by 100 or the total relative abundance (may not be given as %).
- 2. Add up totals.
- 1. Read % abundance from y-axis & Relative isotopic mass from x-axis. Multiply = total relative mass for each isotope.
- Calculating Relative Molecular Mass
- Electronic Structure
- Configuration of Transition Metals
- Chromium and Copper donate a 4s electron to the 3d shell.
- More stable with full or half full d shell.
- Lose 4s electrons before 3d.
- Chromium and Copper donate a 4s electron to the 3d shell.
- Electronic Structure & Chemical Properties
- Outer shell electrons determine chemical properties
- Group 1 & 2 lose electrons and become positive ions
- Group 5, 6 & 7 Gain electrons and become negative ions
- Group 0 doesn't gain or lose electrons so is inert.
- Outer shell electrons determine chemical properties
- Electron Shells
- Each shell given a number called the principal quantum number
- Shells divided into different amounts of sub-shells
- Sub-shells have different amounts of energy (S, P, D, F).
- Sub-shells have different numbers of orbitals that can hold up to two electrons.
- S - 2 electrons P - 6 electrons D - 10 electrons F - 14 electrons
- Sub-shells have different numbers of orbitals that can hold up to two electrons.
- Sub-shells have different amounts of energy (S, P, D, F).
- Working out Configuratio-n
- Showing electron configuration
- Sub-shell notation
- Arrows in boxes
- Energy Level diagram
- Follow Rules
- 1. Fill lowest energy sub-shell first
- 2. Electrons fill sub-shells singularly before sharing
- 3. Configuring ions from s and p block, add or remove from highest energy occupied sub-shell.
- 2. Electrons fill sub-shells singularly before sharing
- 1. Fill lowest energy sub-shell first
- Showing electron configuration
- Configuration of Transition Metals
- Ionisation Energies
- Trends - Group 2
- 1st ionisation energy decreases down group
- Proof for shells. Increased shielding and larger distance between electrons and nucleus.
- 1st ionisation energy decreases down group
- Second IE
- Energy needed to remove 1 electron from 1 mole of gaseous 1+ ions
- Greater than 1st energy as electron is removed from ion instead of an atom.
- Electron configuration plays role in how much larger the 2nd energy is than the 1st
- Energy needed to remove 1 electron from 1 mole of gaseous 1+ ions
- Trends - Across Period
- Across period, general trend is energies increase, due to more protons
- Al & S drop slightly due to starting to fill a new shell with more shielding and a larger distance between the nucleus and outer electrons.
- Drop between groups 5 & 6 is due to electron repulsion
- Across period, general trend is energies increase, due to more protons
- Successive IE
- You can remove all of the atoms from an atom. Each time an electron is removed there is a successive ionisation energy
- Ionisation
- 1st ionisation energy=Energy needed to remove 1 electron from each atom in 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions
- 1. Enter gas symbol, measure for gaseous atoms
- 2. Refer to 1 mole of an atom rather than 1 atom
- 3. Lower ionisation energy = easier to form a positive ion.
- 2. Refer to 1 mole of an atom rather than 1 atom
- Affecting Ionisation Energy
- Nuclear Charge - More protons so stronger attractive force on electrons
- Distance from nucleus - Closer to nucleus means stronger attraction
- Shielding - lessening of pull on outer electrons due to more electrons in inner shells
- IE & Shell Structure
- Can work out how many shells and what group an element is in if you know the successive IEs.
- Within each shell, successful IEs increase as a more positive ion is formed due to less electrons. Big jumps due to new shell
- Number of electrons removed before big jump tells us the group.
- Count number of electrons from right to left until next big jump to tell the number of electrons in each shell. This reveals the element.
- Within each shell, successful IEs increase as a more positive ion is formed due to less electrons. Big jumps due to new shell
- Can work out how many shells and what group an element is in if you know the successive IEs.
- Trends - Group 2
- The Atom
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