What are the basic features of the three subatomic particles?
Generally, which electrons determine the reactivity of an atom?
valence electrons
Which electrons experience the least electrostatic draw to their nucleus?
Which are most likely to form a bond?
Those in the outermost energy level, or shell, called the valence electrons, experience the least electrostatic draw to their nucleus and so are much more likely to become involved in bonds with other atoms (filling empty spaces in other atoms' valence shells)
Avogadro's number
(6.02 × 10^{23}).
amu
mass of one proton is defined as approximately one amu. The size of the atomic mass unit is defined as exactly 1/12 the mass of the carbon12 atom, approximately 1.66 × 10− 24 grams (g).
atomic mass
the mass number (sum of protons and neutrons) of the atom
atomic weight.
mass in grams of one mole of atoms of a given element and is expressed as a ratio of grams per mole (g/mol).
Energy of a Quantam
angular momentum of an electron
Bohr predicted, is quantized according to the following equation:
L = nh/2π
where h is Planck's constant and n is the quantum number, which can be any positive integer. Because the only variable is the quantum number, n, the angular momentum of an electron changes only in discrete amounts with respect to the quantum number.
energy of the electron
Rydberg constant (R_{H})
2.18 × 10^{− 18} J/electron.
ground state
the orbit with the smallest radius in which hydrogen's electron could be found was called the ground state and corresponded to n = 1.
electromagnetic energy
where h is Planck's constant, c is the speed of light in a vacuum (3.00 × 108 m/s), and λ is the wavelength of the radiation.
Balmer series

The group of hydrogen emission lines corresponding to transitions from the upper energy levels n > 2 to n = 2

that is, the pattern of photon emissions from the electron falling from the n > 2 energy level to the n = 2 energy level)

includes four wavelengths in the visible region.
Lyman series
The group corresponding to transitions from the upper energy levels n > 1 to n = 1 (that is, the emissions of photons from the electron falling from the higher energy levels to the ground state) is called the Lyman series, which includes larger energy transitions and therefore shorter photon wavelengths in the UV region of the electromagnetic spectrum.
The energy of the emitted photon corresponds to the precise ________ in energy between the __________ and _____________.
The energy of the emitted photon corresponds to the precise difference in energy between the higherenergy initial state and the lowerenergy final state.
What is Δ E with respect to absorption and emission?
Δ E is the same for absorption or emission between any two energy levels. The sign (positive or negative) of Δ E indicates whether the energy goes in or out and, therefore, whether the electron is going to an excited state (absorption) or to the ground state (emission), respectively.