Found in the nucleus of an atom
Equal to the atomic number (Z)
Characteristics of protons
Mixed with protons = most of an atom’s mass
Equal to the mass number (A) = Protons + This
Characteristics of neutrons
- Atoms that share the same atomic number but have different mass numbers
- Exhibit similar chemical properties
- Differ in their number of neutrons
What is an isotope?
Surround the nucleus at varying distances
If closer to the nucleus, they have lower energies
Characteristics of electrons
- Farthest from the nucleus
- Love bonding and the outside environment
- Least electrostatic pull from the nucleus
- Weak interactions with the nucleus
- Sharing/transferring of these increases stability
Characteristics of valence electrons
Equal to an atom’s mass number
Atomic mass
- The weighted average of isotopes
- Half life can determine proportions of different isotopes
- Avogadro’s #: 6.02*10^23
Atomic weight
- Determines the energy of a quantum
* E=hf, where h is a constant that equals 6.626*10^-34 Js
Plank relation
An atom has a dense, positively charged nucleus that accounts for only a small portion of the atom’s volume
What did Rutherford postulate?
Developed the first quantum theory that says energy that’s given off as electromagnetic radiation from matter comes in bundles (quaunta)
What did Planck postulate?
The centripetal force acting on the electron as it revolved around the nucleus was created by the electrostatic force between the positively charged proton and the negatively charged electron.
Electrons follow a clearly defined pathway
What did Bohr postulate?
Bohr’s equations
Angular momentum: L=nh/2pi
Electron energy: E=-RH/n^2 where RH=2.18*10^-18 Js
*Energy is directly proportional to the principal quantum number (n)
- The state of lowest energy for an atom in which all electrons are in the lowest possible orbitals
- Most likely will happen at room temperature
What is ground state?
- At least one electron has moved to a subshell of higher than normal energy
- Can be excited through heat and to different energy levels
- Results in energy absorption at specific wavelengths (absorption spectrum)
What is excited state?
How do you determine the electromagnetic energy of photons?
E=hc/wavelength, where c is the speed of light = (3.00*10^8 m/s)
Line spectrum: each line of the spectrum relates to a specific electron transition
Atomic emission spectrum: can be used as a fingerprint for an element; hydrogen is the simplest
Atomic emissions
What are the different transitions to energy levels?
Lyman series: n greater/equal to 2 to n=2, which has larger transitions and shorter photon wavelengths
Balmer series: n greater/equal to 3 to n=3, which has 4 wavelengths in the visible region
Paschen series: n greater/equal to 4 to n=3
What is the Heisenburg uncertainty principle?
It’s impossible to determine the momentum and position of an electron simultaneously
What is the Pauli exclusion principle?
No two electrons in an atom can have the same set of 4 quantum numbers
Position and energy of an electron by its quantum numbers = energy state
Characteristics of the principal quantum number
- “n”
- The larger the n, the higher the energy level and radius of an electron’s shell
- Maximum # of electrons in a shell: 2n^2
- The difference in energy b/w 2 shell decrease as the distance from the nucleus increases
Characteristics of the azimuthal quantum number
“l”
- Refers to size and number of subshells
- To find l in relation to n, l= n-1 (ex: n=1, l=0; n=2, l=0 and1)
- l=0= s subshell, l=1=p subshell, l=2=d subshell, l=3=f subshell
- Maximum # of electrons in a subshell: 4l+2
Characteristics of the magnetic quantum number
“ml”
- Specifies the particular orbital
- For any possible values of l, ml= 2l+1 (ex: l=1, ml= -1, 0, 1)
Shape of subshells
s: spherical
p: dumbbell
Characteristics of the spin quantum number
“ms”
- Two spin orientation: -1/2 or 1/2
- If electrons are in the same orbital, they spin oppositely (paired)
- If electrons are in different orbital, ms values will be the same (parallel)
