Be sure to keep up on your reading from your text and
studying your notes (scientific method, sigfigs, sci.
notation, electron configs, models, etc.). A quiz may be
right around the corner… Or not… Or yes… Hint hint.
Electrons (e-’s) and Orbitals

Several models were created to explain the
properties observed by the atom.
◦ The charges of the electrons
◦ The charges of the protons
◦ The size, locations, and arrangement

Originally, scientists believed (chronologically)
1. Solid-Sphere Model (Plum Pudding Model)
2. Planetary Model (Rutherford’s Model)
3. Quantum Model (WHAT WE KNOW TODAY)

Rutherford’s model proposed electrons orbit
the atom
◦ This proved J. J. Thompson’s “Plum Pudding Model”
was incorrect
◦ States electrons orbited the atom like moons to a
planet

Bohr’s model confines e-’s to energy levels
◦ States e-’s can only be certain distances from the
nucleus
◦ This distance depends on the energy the e- has
◦ The further away, the higher energy level

The present-day model of the atom, in which
electrons are located in orbitals, is also
known as the quantum model
◦ States electrons within an energy level are located
in orbitals, regions of high probability for finding a
particular electrons.
◦ Does not, however, explain how the electrons move
about the nucleus to create these regions

According to the current model of the atom,
electrons are found in orbitals
◦ -regions around the nucleus that correspond to
specific energy levels
◦ Orbitals are sometimes called electron clouds
because they do not have sharp boundaries
◦ Tells where it is likely to find an electron

Pauli Exclusion Principle
◦ The principle that states that two particles of a
certain class cannot be in the exact same energy
state

Electron Configuration
◦ the arrangement of electrons in an atom

Aufbau Principle (German for “building up”)
◦ States that electrons fill orbitals that have the
lowest energy first!!



“Building up” refers to the filling of all lower
energy “sites” before increasing up in energy
Moving outward away from the (+) nucleus
requires more energy for the (-) electrons to
maintain the further distance
We have 4 orbitals (spots) that e-’s can go into:
◦ s-orbital (holds ________)
◦ p-orbital (holds ________)
d-orbital (holds ________)
f-orbital (holds ________)

Write out the electron configuration for an
element with an atomic number of 20
Atomic # = # of protons = # of electrons
1s22s22p63s23p64s2
We can abbreviate this using the LAST noble gas
i.e. [Ar] 4s2



Write the electron configuration for an atom of an
element whose atomic number is 8.
Write the electron configuration for an atoms of an
element whose atomic number is 34.
Write out the electron configuration for Copper.


Draw these out.
Electrons MUST fill the lower energy levels
before moving to the next. Each level is
increasing energy.

If an electron is in a state of lowest possible
energy it is in the Ground State

If an electron gains energy, it moves to an
Excited State

An electron in an excited state will release a
specific amount of energy as it “falls” back
down to the ground state.
◦ This energy is emitted as certain wavelengths of
light

Atomic Mass
◦ The mass of an atoms expressed in atomic mass
units (AMU)

The Mole!!
◦ A mole is just a counting unit (a quantity) for really
small things (like atoms)
◦ It is 6.0221367 x 1023 of anything
◦ This value is known as Avogadro’s Number

Molar Mass
◦ The mass in grams of one mole of the element
◦ Has the units of g/mol


1 mole has 6.022x1023 atoms (particles)
Avogadro’s Number allows us to CONVERT
between moles and grams

Calculate the molar mass of NH3

Calculate the molar mass of H2SO4

Calculate the molar mass of NaCl

Convert 12.5 grams of LiOH to moles LiOH

Convert 0.58 moles of H2O to atoms of water

Convert 1.28 moles of cobalt(II)oxide to mass

Counting Atoms and Electron Configuration
Worksheet

Work on:


e- config for Mn,
Fe, and Co
Convert:
◦ 1.85 mol Al  g
◦ 8.9 g O  mols