Glencoe Chapters 4, 5, and 24

Atoms: The smallest component of an element having the chemical properties of that element

The three best-known subatomic particles are represented as follows: ParticleSymbol Mass Charge Neutron n x kg none Proton p x kg positive Electron e x kg negative

 Protons and neutrons are in the nucleus  Electrons are in a “cloud” surrounding the nucleus  Atomic Number:  Represents the number of protons in an atom  Example: Carbon (C) has 6 protons  Elements differ by their atomic number

 Mass Number (atomic mass):  Represents the number of protons and neutrons in an atom  Ex: carbon has a mass number of  Isotopes:  Atoms of an element that contain different numbers of neutrons  All elements have isotopes

 Atomic mass is an average of the masses of all available isotopes of the element, based on percent occurrence  Nomenclature to distinguish isotopes:  C-12 is “carbon twelve” ◦ ______ protons and ______ neutrons  C-14 is “carbon fourteen” ◦ ______ protons and ______ neutrons

 Nuclear chemistry:  Deals with radioactivity, nuclear processes and nuclear properties  Nuclear stability: depends on the neutron to proton ratio  Band of stability:  Ratio from 1.0 to 1.5 where all isotopes are stable  Any isotope outside the band is unstable

 Radioactivity:  The spontaneous emission of high energy particles or rays by unstable atomic nuclei to form stable nuclei  All transuranium elements are radioactive  Nucleic decay produces alpha particles, beta particles, or gamma rays

 Alpha particles (α):  Represented by 4 2 He  +2 charge  Are high speed helium nuclei  “Safest” of the basic forms of radioactivity  Fairly low penetrating power (can be stopped by paper)

 Beta Particles (β or e-) :  Represented by 0 -1 e  High speed electrons  -1charge  Fairly high penetrating power (stopped by foil, clothing)

 Gamma Rays ( γ) :  Represented by 0 0 γ  High energy electromagnetic waves  No charge  Extremely high penetrating power (lead and concrete will not completely block)  Very dangerous form of radiation

 Written as equations  mass numbers (superscripts)  atomic numbers (subscripts)  Superscripts and subscripts must equal on both sides of the equation

 Examples:  Alpha decay:   92 U → 90 Th + 2 He γ  Beta decay:   53 I → 54 Xe + -1 e

 Positron emission  Electron capture:

 Examples (continued):  Neutron bombardment * :   92 U + 0 n → 92 U  * Is different because it makes a less stable nucleus while all the other types of decay make a more stable nucleus. (used to initiate chain reactions in nuclear power plants)

 A sequence of decay reactions that occur spontaneously. Intermediate products are unstable and the process will continue until a stable product is formed.  Example:  Decay series: ◦ 1. Alpha decay of U-235 followed by ◦ 2. Beta decay of product from step 1 followed by ◦ 3. Alpha decay of product from step 2

 Each radioactive isotope has a half life ◦ The time it takes for half the mass of an available sample to decay into another substance.  Half-life can be used to: ◦ calculate how long it would take to result in a level of the isotope that could be tolerated by living things ◦ calculate the mass of an isotope remaining after a period of time. m final = m initial x.5 t/T  t = amount of time that has passed  T = length of the half-life

Example: How much of a 25.0g sample of radon-222 will remain after 30 days if the half life of radon-222 is 10 days? m final = m initial x.5 t/T t/T = 30days/10days = 3.0 m final = 25.0g x (.5) 3 = 3.125g More Examples

 Two sources:  Fission:  The splitting of nuclei to release energy  Neutrons are used to initiate the process  Fission reaction is self-sustaining  Currently used in nuclear power plants  Problems?

 Fusion:  Combining nuclei (hydrogen isotopes combine to form helium)  Occurs on the sun and other stars  More powerful process than fission  Problems?

 Development of the modern atomic theory – see handout. Study as part of lecture packet. This will be part of the unit exam. A group project is also from this material.

The quantum mechanical model of the atom is based on the study of waves and light. Definitions: Amplitude – the distance from the crest to the midway origin line of the wave

Wavelength ( ): the distance between similar points in a set of waves (crest to crest or trough to trough) Measured in meters Frequency ( ) the number of waves that pass a given point per unit time Measured in cycles/second (sec -1 ) Usually called a Hertz (Hz)

Frequency, wavelength, and energy are related: c = andE = h = wavelength = frequency c = the speed of light in a vacuum (3.00x10 8 m/s) h = Planck’s constant (6.626x J/Hz) E = energy

Electromagnetic Radiation (EMR) – a form of energy that travels in waves. Includes all visible light and other forms of wave energy:

 All EMR is the result of electron movement between energy levels within atoms  Electrons absorb energy to reach higher (excited) energy state  Energy is absorbed and emitted in the form of photons  Photons: discrete “packets” of energy

 Bright Line Spectrum:  Distinct lines of color that correspond to wavelengths, frequencies, and energies specific to each individual element  Can be used to identify elements

 Research by Louis deBroglie and Erwin Schrodinger led to the branch of physics called quantum mechanics.  Current atomic models are based on quantum mechanics and probability  Probability is the statistical likelihood of an occurrence  Heisenberg Uncertainty Principle: states that it is not possible to know both the position and the speed of an electron at the same time

Schrodinger developed an equation to describe electron location and behavior – uses quantum numbers

n = Principle Quantum Number  refers to the energy level location of the electron  Can be from 1-7

 l = Orbital Quantum Number  refers to the sublevel location of the electron  Can be s, p, d, or f

 s orbitals: ◦ Spherical shape ◦ Lowest energy ◦ Closest to the nucleus ◦ One per energy level  p orbitals: ◦ Figure 8 shape ◦ Higher energy ◦ Further from the nucleus ◦ Three per energy level starting with 2nd

 d orbitals: ◦ Cloverleaf shape ◦ Even higher energy ◦ Even further from the nucleus ◦ Five per energy level starting with 3rd  f orbitals: ◦ Very complex shape ◦ Highest energy ◦ Furthest from the nucleus ◦ Seven per energy level starting with 4th

 m l = Magnetic Quantum Number ◦ designates the number of orbitals on each sublevel ◦ designates in which specific orbital the electron is likely located  m s = Spin Quantum Number ◦ describes the direction of spin for the electron ◦ is either clockwise or counter-clockwise

 Basic Rules:  Aufbau Principle – electrons enter lowest energy levels first  Hund’s Rule – each orbital in a sublevel is occupied by one electron before any orbital obtains two electrons  All electrons in singly occupied orbitals have the same spin directions

 Basic Rules (continued):  The Pauli Exclusion Principle: ◦ No more than 2 electrons may occupy any one orbital ◦ Electrons that occupy the same orbital must have opposite spins ◦ No two electrons in one atom will have the same the four quantum numbers

 Use the basic rules and basic arrangement of the periodic table: ◦ Row number ◦ Position in row ◦ s, p, d, and f blocks

 Electron Configuration Notation, Orbital  Diagrams, Noble Gas Shorthand, and Lewis  Dot Structures for each of the following. Include in your lecture packet to study.  Use this:  1s  2s2p  3s3p 3d  4s4p 4d 4f  5s5p 5d 5f  6s6p 6d 6f  7s7p 7d 7f

 Orbital Diagrams:  HNaFe  HeMgCu  LiP  BeS  BCl  CCa  NSc  OV  FNi  NeZn

 Electron Configuration Notation:  HNaFe  HeMgCu  LiP  BeS  BCl  CCa  NSc  OV  FNi  NeZn

 Noble Gas Shorthand:  HNaFe  HeMgCu  LiP  BeS  BCl  CCa  NSc  OV  FNi  NeZn

 Lewis Dot Structures:  HNaFe  HeMgCu  LiP  BeS  BCl  CCa  NSc  OV  FNi  NeZn