• Kinetic and potential energy are interconvertible-one can be converted to the other
• Energy can assume many forms, the total energy of the universe is constant.
• Energy can neither be created nor destroyed.
• When the energy of one form disappears, the same amount of energy reappears in another form or forms. 

• A quantum of energy is the smallest quantity of every that can be emitted (or absorbed)

The Line Spectrum of Hydrogen

• Neils Bohr attributed the emission of radiation by an energized hydrogen atom to the electron dropping from a higher-energy orbit to a lower one.
• As the electron dropped, it gave up a quantum of energy in the form of light.
• Bohr showed that the energies of the electron in a hydrogen atom are given by the equation:
  • En is the energy
  • n is a positive integer
• As an electron gets closer to the nucleus, n decreases.
• En becomes larger in absolute value (but more negative) as n gets smaller. 

• The Heisenberg uncertainty principle states that it is impossible to know simultaneously both the momentum p and the position x of a particle with certainty.
• *look at equations* 
• x is the uncertainty in position in meters
• p is the uncertainty in momentum
• u is the uncertainty in velocity in m/s
• m is the mass in kg

• Erwin Schrödinger derived a complex mathematical formula to incorporate the wave and particle characteristics of electrons.
• Wave behavior is described with the wave function ψ.
• The probability of finding an electron in a certain area of space is proportional to ψ2andis called electron density.

• The Schrödinger equation specifies possible energy states an electron can occupy in a hydrogen atom.
• The energy states and wave functions are characterized by a set of quantum numbers.
• Instead of referring to orbitsas in the Bohr model, quantum numbers and wave functions describe atomic orbitals

• Energy is the capacity to do work or transfer heat.
• All forms of energy are either kinetic or potential.
  • Kinetic energy (Ek)is the energy of motion.
  • *find equation*
    • m is the mass of the object
    • u is its velocity
  • One form of kinetic energy of particular interest to chemists is thermal energy, which is the energy associated with the random motion of atoms and molecules.

• Visible light is only a small component of the continuum of radiant energy known as the electromagnetic spectrum.
• All forms of electromagnetic radiation travel in waves.
• Waves are characterized by:
  • Wavelength(λ; lambda) – the distance between  identical points on successive waves
  • Frequency (ν; nu) – the number of waves that pass through a particular point in 1 second.
  • Amplitude – the vertical distance from the midline of a wave to the top of the peak or the bottom of the trough.
• An electromagnetic wave has both an electric field component and a magnetic component. The electric and magnetic components have the same frequency and wavelength.

Blackbody Radiation (know the process)

• When a solid is heated, it emits electromagnetic radiation, known as blackbody radiation, over a wide range of wavelengths.
• The amount of energy given off at a certain temperature depends on the wavelength.
• Classical physics failed to completely explain the phenomenon.
  • Assumed that radiant energy was continuous; that is, could be emitted or absorbed in any amount.
• Max Planck suggested that radiant energy is only emitted or absorbed in discrete quantities, like small packages or bundles.

• Quantum numbers are required to describe the distribution of electron density in an atom.
• There are three quantum numbers necessary to describe an atomic orbital.
  1. The principal quantum number (n) – designates size
  2. The angular moment quantum number (l) – describes shape
  3. The magnetic quantum number (ml) – specifies orientation3.7
• The principal quantum number (n) designates the size of the orbital.
  • Larger values of n correspond to larger orbitals.
  • The allowed values of n are integral numbers: 1, 2, 3 and so forth.
  • The value of n corresponds to the value of n in Bohr’s model of the hydrogen atom.
  • A collection of orbitals with the same value of n is frequently called a shell

• The angular moment quantum number(l) describes the shape of the orbital.
• The values of l are integers that depend on the value of the principal quantum number
• The allowed values of l range from 0 to n – 1.
  • Example: If n = 2, l can be 0 or 1.
• A collection of orbitals with the same value of n and l is referred to as a subshell.

• The magnetic quantum number (ml) describes the orientation of the orbital in space.
• The values of ml are integers that depend on the value of the angular moment quantum number:– l,...0,...+l

• In 1864, John Newlands noted that when the elements were arranged in order of atomic mass that every eighth element had similar properties.

  ØHe referred to this as the law of octaves.
• In 1869, Dmitri Mendeleev and Lothar Meyer independently proposed the idea of periodicity.
• Mendeleev grouped elements (66) according to properties.
• Mendeleev predicted properties for elements not yet discovered, such as Ga.
• However, Mendeleev could not explain inconsistencies such as argon coming before potassium in the periodic table, despite having a higher atomic mass.
• In 1913, Henry Moseley discovered the correlation between the number of protons (atomic number) and the frequency of X-rays generated.
• Ordering the periodic table by atomic number instead of atomic mass enabled scientists to make sense of discrepancies.
• Entries today include atomic number and symbol; and are arranged according to electron configuration.

Valence electrons

• The outermost electrons of an atom are called the valence electrons.
• Valence electrons are involved in the formation of chemical bonds.
• The similarity of valence electron configurations helps predict chemical properties.
• *look at PP for more info*

• Effective nuclear charge (Zeff) is the actual magnitude of positive charge that is “experienced” by an electron in the atom.

• Ionization energy (IE) is the minimum energy required to remove an electron from an atom in the gas phase.
• The result is an ion, a chemical species with a net charge.
• Sodium has an ionization energy of 495.8 kJ/mol.
  
• Specifically, 495.8 kJ/mol is the first ionization energy of sodium, IE1(Na), which corresponds to the removal of the most loosely held electron.
• *Lots more on PP*

The result is an ion, a chemical species with a net charge.

• Electron affinity (EA) is the energy released when an atom in the gas phase accepts an electron. 
• Like ionization energy, electron affinity increases from left to right across a period as Zeff increases. -Easier to add an electron as the positive charge of the nucleus increases.

• An isoelectronic series is a series of two or more species that have identical electron configurations, but different nuclear charges.

• However, Mendeleev could not explain inconsistencies such as argon coming before potassium in the periodic table, despite having a higher atomic mass.
• In 1913, Henry Moseley discovered the correlation between the number of protons (atomic number) and frequency of X-rays generated.
• Ordering the periodic table by atomic number instead of atomic mass enabled scientists to make sense of discrepancies.

Entries today include atomic number and symbol; and are arranged according to electron configuration.

Diagram each of the periodic trends: Atomic Radius, Ionization energy, Electron Affinity, Metallic Character, and Ionic Radius

• En is most negative when n = 1.
  • Called the ground state, the lowest energy state of the atom
  • For hydrogen, this is the most stable state
• The stability of the electron decreases as n increases.
• Each energy state in which n > 1 is called an excited state.
• Radiant energy absorbed by the atom causes the electron to move from the ground state (n = 1) to an excited state (n > 1).

• Quantum numbers are required to describe the distribution of electron density in an atom.
• There are three quantum numbers necessary to describe an atomic orbital.
  1. The principal quantum number (n) – designates size
  2. The angular moment quantum number (l) – describes shape
  3. The magnetic quantum number (ml) – specifies orientation

• Potential energy is the energy possessed by an object by virtue of its position.
• There are two forms of potential energy of great interest to chemists:
  1. Chemical energy is energy stored within the structural units of chemical substances.
  2. Electrostatic energy is potential energy that results from the interaction of charged particles.
• *find equation*
• Q1and Q2 represent two charges separated by the distance, d.