Atomic Structure Unit Study Guide
The topics covered during this unit have been:
History of the atom (how we have come to understand the structure)
You will need to know the contributors to the atomic structure and their models…
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Democritus
Aristotle
John Dalton
J.J. Thompson
Ernest Rutherford
Neils Bohr
Parts of the nucleus
We have studied over the unit how to recognize each element using the periodic table and its
parts that make up the nucleus. The two particles in particular are the proton and the neutron.
The proton, remember, is the only part of the atom that tell us what type of element an atom
is. The proton has a positive charge. The neutron does not. We always recognize both in our
diagrams of the atom, such as the bohr diagram. The two particles also are the only particles
that contribute to the mass of the atom. Each one has a mass of 1 amu. This unit is a whole
number. When we use the average atomic mass to find the amount of neutron are typically in
any type of atom we must round to the nearest whole number.
Isotopes
Isotopes are variations of an element that differ because of the number of neutrons that are
present in the nucleus. The typical notation for an isotope is the name of the element followed
by a hyphen and the value of the atomic mass, such as carbon-14. Isotopes are the reason why
average atomic masses are not an even number. We take into account the percentages of every
isotope of an element and then factor that in to the average atomic mass represented by all the
possible masses of the element.
Electrons
 Electrons- Energy levels, sublevels, and orbitals.
 Electron Notation- How we describe and notate the electrons in a certain atom.
 Valence Electrons- The outside electrons that are the most actually interact with their
surroundings and participate in most bonding.
 Periodic trends- Electronegativity, atomic radius, and ionization energy
We took a close look at how electrons situate themselves around their nucleus. We learned
how there were different levels and in the levels there were even more specific sublevels. For
every electron around a nucleus there is a specific energy level, sublevel, orbit and spin
assigned to it. We use these to help us understand where electrons are around our atom and
how they will affect the way the atom interacts with other atoms and matter it comes in
contact with. We know how this looks on a Bohr diagram or Lewis Dot Structure ( see power
point on web site) and also how we assign these electrons in proper notation.
Electron notation
We have 3 different ways to notate electron around an atom
1. Orbital notation
2. Electron configuration
1s22s22p63s23p6………….
3. Abbreviated electron configuration, remember go back to the last noble gas, not the
next element!!
Li = [He]2s1
Valence Electrons
Valence electrons are the electrons that are in an incomplete energy level and that directly
affect bonding between atoms. We must always take into account these electrons, because
they are the part of the atoms structure that contributes to the ways in which they react and
their chemical properties.