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PDP ChemistryAtomic structure
Topic 2: Atomic structure
• solids, liquids and gases• pressure volume and temperature
in a gas• models of the atom• subatomic particles• electron arrangement• converting units• measuring chemical quantities
Phases of matterHow do we classify matter?
Particles in solids, liquids and gases
Think Pair Share
Size of an atom
How big is a carbon atom?
stearic acid monolayer
1% stearic acid solution
Modelling a cylinder V = πr2h
Why are we uncertain about the result?
Percentage uncertainties: How much do we know what we don’t know?
percentage uncertainty = uncertainty/value x 100
for example 20±2cm
% uncertainty = 2/20 x 100 = 10%
sig figs!
Quantifiable uncertainties in size of a carbon atom
Variable Value Absolute uncertainty
% uncertainty
What other factors affect how accurate your result is?
Factor affecting accuracy Does it make the final result higher or lower?
Carbon atom
Image: ttp://salihabava.com/2012/10/we-create-in-play/.
Covalent radiussp3: 77 pmsp2: 73 pmsp: 69 pm
Van der Waals radius 170 pm
1pm = 10-12m
They’re much too small to see so how do we know atoms exist? And how do we know what they’re made of?
H2
O
How do we know about atoms?
Atoms
substances combine in fixed ratios
kinetic theory of solids, liquids and gases
scanning tunneling microscopy
Brownian motion
Atomic structure
cathode rays
Geiger-Marsden gold foil experiment
emission spectra
radioactivity
particle accelerators
How do we know about atoms?
Combination in fixed ratios
2g of hydrogen and 16g of oxygen make 18g of water
4g of hydrogen and 32g of oxygen make 36g of water
H2
O
Kinetic theory- microscopic model to explain macroscopic properties
Melting and boilingCompressibilityPouring
Brownian motion
Image: https://en.wikipedia.org/wiki/Brownian_motion
Brownian motion YT from 4 min
Scanning tunnelling microscope images
Iron atoms on copper, Image: http://www.almaden.ibm.com/vis/stm/atomo.html
How do we know about atomic structure?
Cathode rays
Geiger-Marsden gold foil experiment
Radioactivity
Emission spectra
https://en.wikipedia.org/wiki/Balmer_series, https://en.wikipedia.org/wiki/Flame_test
Particle accelerators
Image: https://en.wikipedia.org/wiki/Particle_accelerator
How is an atom structured?
Atomic structure PEN
ChargeProton charge = 1.602176565 × 10−19 CNeutron charge = 0Electron charge = −1.602176565 × 10−19C
MassProton mass = 1.67262158 × 10-27 kgNeutron mass = 1.674927352 × 10−27 kgElectron mass = 9.10938291 × 10−31kg
Simpler units
relative charge proton = +1
electron = -1
relative mass proton = 1.007 u (unified atomic mass unit)
neutron = 1.008 u
electron = 0.000 5485 u
Atomic number (Z) is the number of protons in the nucleus
Mass number (A) is the number of nucleons (protons + neutrons)
Isotopes are atoms of the same element with different numbers of neutrons (and a different mass number)
LiMass number 7
Atomic number 3
Atomic mass (atomic weight)
How are electrons arranged around an atom?
Models of the atom
Bohr model
Emission spectra
energy emitted as photons when electrons move between energy levelshf
Ionization energy
1 5 9 13 17 21 25 29 33 37 41 45 49 53 57 61 65 69 73 77 81 85 89 93 970
500
1000
1500
2000
2500
Ionization energies of the first 100 elements
Atomic number
Ioniz
ati
on e
nerg
y k
Jmol-1
Electrons arranged in shells
Image: https://en.wikipedia.org/wiki/Periodic_table
Periodic table and electron shells
Standard periodic table
Image: https://en.wikipedia.org/wiki/Periodic_table
Newland’s PT, 1866
Image: https://en.wikipedia.org/wiki/Periodic_table
Mendeleev’s PT, 1869
Image: https://en.wikipedia.org/wiki/Periodic_table
Spiral PT,modern
Image: https://en.wikipedia.org/wiki/Periodic_table
List the physical and chemical properties of A,B,C,D and E
www.webelements.com
Write at least 5 sentences about how the periodic table is arranged.
Image: https://en.wikipedia.org/wiki/Periodic_table
Periodicity
Trends in the periodic table
Image: https://en.wikipedia.org/wiki/Periodic_trends
Important groups
1. Alkali metals
2. Alkali earths
17. Halogens
18. Noble gases
