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