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32 Cards in this Set

  • Front
  • Back
Def. of Atom
- smallest unit of matter;
Democritus’ Atomic Philosophy-
-atoms were indivisible, indestructible
-matter composed of indivisible particles and empty space
Dalton’s Atomic Theory- The Postulates
1. All matter consists of atoms
2. Atoms of one element can’t be converted to atoms of another
3. Atoms of an element are identical in mass but different than another element
4. Compounds result from chemical combination of specific ratio of atoms
Dalton's theory explains mass laws
- atoms can’t be created/destroyed, or converted to different types of atoms,
-every atom has fixed mass, chem.
-Reaction atoms are combined but mass doesn’t change
Modern Atomic Theory
1. All matter composed of atoms
2. Atoms cannot be subdivide, created, destroyed except in nuclear reactions
3. Atoms of an element differ in proportion from atoms of another element
4. Atoms of an element have a characteristic average mass unique to element
Discovery of the Electron
-J J Thomson, 1897 used cathode ray tube to deduce the presence of negative charged particle (electron)
Mass of Electron
-Robert Milliken 1909 determines mass of electron 9.109 time 10^-31
Atomic Scale
-Most mass of atom is in nucleus, electrons are found in outside of nucleus,
Thomason’s Atomic Model
-believed that electrons were like plums embedded in a positively charged “pudding”
who discovered nucleus
Rutherford- bounced off of gold leaf, something else in atom besides electrons (nucleus is small and dense,
Atomic Number-
(Z) tells the number of protons and electrons in the element
Mass Number-
(A) number of protons and neutrons in nucleus of an isotope
- elements have natural mixtures of isotopes; atoms of same element that different in number of neutrons
Atomic mass is an...
-average of naturally occurring isotopes of that element
-Find: (atomic mass) (percent) + (atomic mass) (percent)= average
Bohr Model of the Atom
- electrons orbit nucleus like planets orbit sun
1. The H atom has only certain allowable energy levels
2. The atom does not radiate energy while in one of its stationary states
3. The atom changes to another stationary state (electron moves to another orbit) absorbing or emitting a photon
Noble gases
the 6 of them
use them for
-all shells are filled stable (He, Ne, Ar, Kr, Xe, Rn)
- use noble gas closer to another gas
Bohr Limitations
- failed to predict spectrum of any atom beside H
-only works for one electron species;
Quantum Mechanical model-
-describes an atom with certain allowed wave like motion of an electron whose exact location is impossible to know
has a meaning...
-region within an atom w/ a probability of finding an electron;
-shapes defines surface w/ 90% of a total electron;
-mathematical function with no physical meaning
Quantum Numbers
- gives electron identity (4)
Principal quantum number-
letter symbol
-denotes shell level where electron is located,
-number of electrons- 2n^2
Angular momentum (l)
-shapes of the orbital sub shell in which electron is located
shapes of
s-shaped (sphere)
p-shaped (peanut)
Magnetic quantum number-
letter symbol
-denotes orientation of the electron orbital w/ respect to 3 axis in space
-(sphere lies on all 3 axis)
to find each of these
Angular momentum l (shape)
Magnetic (orientation)
Spin Quantum number
0 -> n-1
–L, 0, +L
½ and -½
Aufbau Principle
- Electrons are added one at a time to the lowest energy orbital- go up to 2 electrons
Pauli Exclusion Principal
- orbital holds 2 electrons and spins in opposite direction
Hund’s rule
- electron occupies equal energy orbital; electrons go into one orbital before pairing
Transition elements-
Irregular configuration Cr and Cu
one electron in an orbital is more stable than a full orbital
electrons in each shape
Order of orbitals
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d
energy level sets
|2s, 2p|
|3s, 3p|
|4s, 3d, 4p|
|5s, 4d, 5p|
|6s, 4f, 5d, 6p|
|7s, 5f, 6d|