Chapter 2 Atomic Structure

Law of Conservation of Mass Mass can be The total mass of the

Law of Constant Composition Water is water, no matter where you get it; H 2 O is H 2 O The elements in a compound are present in a

Percent Composition Percent by mass of an element in a compound. –

Practice Determine the percent composition of calcium phosphate, Ca 3 (PO 4 ) 2.

Dalton’s Theory All matter is composed of The atoms of any one element are. Atoms of different elements have different masses. Compounds are In reactions, atoms are exchanged to form new compounds.

Atomic masses Relative. Based on carbon-12. Isotopes. Mass numbers on Table reflect abundance of isotopes.

Atomic Number Tells you… 1 H

Structure Protons – Neutron – Electron –

Mass Number Tells you – – H

Calcium Atomic number = – What is the charge?

Ions Gain or lose – Octet Rule: –

Calcium Ion Has ‘lost’ 2 electrons What is the charge?

Sulfide Ion Has gained two electrons What is the charge?

Isotopes Identified by mass number C-12, C-13 Alternate notation – – C 12 6

Determining Average Mass Ave = (mass of isotope 1 x % abundance as a decimal) + (mass of isotope 2 x % abundance as a decimal) H-1 = 99% H-2 = 0.88% H-3 = 0.12%

Average Atomic Mass What is the average mass of element Q? The abundances are: –Q-54 42% –Q-52 20% –Q-57 10% –Q-58 28%

Periodic Table Label appropriately… Properties of elements Tables 2.2 and 2.3 Explained by organization in atom

Electromagnetic Radiation Electromagnetic spectrum Radio waves  cosmic rays Visible light is small portion

Electromagnetic Radiation Speed of light in air  Electromagnetic radiation moves through a vacuum at speed of Since light moves at constant speed there is a relationship between wavelength and frequency: Wavelength and frequency are inversely proportional

Practice What is the wavelength of light that has a frequency of 2.51 x s -1 ?

Electromagnetic Spectrum

Emission Spectra See figure 2.10, p 51 Radiation emitted by an ‘excited’ atom Color is specific to the atom Fireworks

Line Spectrum Elements in gaseous states give off colored light –High temperature or high voltage –Always the same –Each element is unique Spectra

Line Spectrum Ground state – Excited state – –Farther from nucleus –

Line Spectrum Electron falls from higher energy level to lower Color of light emitted depends on difference

Line Spectrum Each band of color is produced by light of a different Each particular wavelength has a definite Each line must therefore be produced by emission of

Absorption Spectra Radiation Used as a tool to measure concentration

Model of the Atom Niels Bohr Solar system model Explains Hydrogen

The Bohr Atom Model didn’t seem to work with atoms with more than one electron Did not explain chemical behavior of the atoms

Beginnings… Max Planck ( ) –Proposed that there is a fundamental restriction on the amounts of energy that an object emits or absorbs, Energy is released in

Beginnings A quantum is a finite quantity of energy that can be gained or lost by an atom E = v = h = x J/s This constant, h, is the same for all electromagnetic radiation

Practice Determine the energy of light with a frequency of 2.22 x Hz

Quantum numbers There are 4 Tell you how

Principal Quantum Number The first quantum number Corresponds to the Value of Symbolized by n

Azimuthal Quantum Number The second quantum number Tells you the Symbolized by l Has values of 0 to n-1 Usually shown as

Orbitals Each sublevel (orbital) has a specific shape

Quantum Numbers Orbital Quantum Number: –Indicates the shape of an orbital –(subshell or sublevels) –s, p, d, f Principal Quantum #Orbital Quantum # 11s 22s, 2p 33s, 3p, 3d 44s, 4p, 4d, 4f

Magnetic Quantum Number The third number Tells you the Has values of +l to -l

Orbitron For a full view of the different orbital shapes, visit /index.htmlhttp:// /index.html

Spin Quantum Number Final quantum number Electrons behave like little magnets (spin gives magnetism) Value of + or – ½ or…

Putting it all together Table 2.6 and 2.7 Orbital arrangement on the periodic table Electron configuration Aufbau principal –“Building up’

Pauli Exclusion Principal No more than No electron can have the

Hund’s Rule Electrons will fill Applies to p, d, and f orbitals Electrons (little magnets) repel each other if they have the same spin

Rules for Orbital Filling Pauli’s Exclusion Rule – Hund’s Rule – 1s 2s 2p 3s 3p

Rules for Orbital Filling Aufbau –The order of fillingis from the bottom (low energy) up –Due to energy levels

Rules for Orbital Filling Diagonal Rule The order of filling once the d & f sublevels are being filled Due to energy levels

Quantum Numbers Spin Quantum Number: –Indicates two possible states of an electron in an orbital Type of OrbitalNumber of Orbitals s1 () p3 (x, y, z) (,,,) d5 (,,,, ) f7f7 Each orbital holds a maximum of 2 electrons

Application of Quantum Numbers Several ways of writing the address or location of an electron Lowest energy levels are filled first Electron Configuration: using the diagonal rule, the principal quantum number (n), and the sublevel write out the location of all electrons 12 C: 32 S: 1s 2 2s 2 2p 6 3s 2 3p 4 1s 2 2s 2 2p 2

Application of Quantum Numbers Orbital filling electron diagram: using Hund’s rule and the diagonal rule write out the location of all electrons See examples on whiteboard

Chapter 1 States of matter Classification of substances –Mixtures –Pure substances, etc Methods of separation of mixtures

Chapter 1 Measurement Units Conversions Significant figures, calculations

Chapter 1 Density and calculations Temperature and conversions Specific heat and calculations

Chapter 2 Dalton’s ideas Percent composition Interpretation of the table –Masses, atomic number, etc Isotopes and average weighted mass

Chapter 2 Quantum numbers Orbitals How to put them together…