Understanding the Atom_OLD
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Contents: Chapter 2: Quantum Theory, Orbits vs. Orbitals, Orbital Shapes, Electron Configuration Diagram. Chapter 3: Writing Full Electron Configurations and Diagrams, Aufbau Rule, Hünd's Rule, Pauli Principle, and Connection between Periodic Table and Order of Filling for Electrons, Many Examples Worked for the Student. Narration: William R. Sponholtz, III, B.S., M.S., PH.D. Full DVD available at http://sponholtzproductions.comIncludes: Chapter 1: Protons, Neutrons, Electrons, Strong Nuclear Force, Ions, Cations, Anions, Mass Number, Atomic Mass, Atomic Number, Isotopes, Nucleus, and Relative Size of Atom, Many Examples and Calculations Worked for the Student. Chapter 4: Writing Abbreviated Electron Configurations and Diagrams, Noble Core and Valence Electrons, Many Examples Worked for the Student. Chapter 5: Determining the Four Quantum Numbers (Principle, Angular Momentum, Magnetic, and Spin Quantum Number), Many Examples Worked for the Student.
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[Music]
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in the early 1900's many brilliant minds
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were changing the landscape of science
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in particular quantum theory was
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emerging and changing the way we viewed
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the atom one of the great results of
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quantum mechanics was the orbital which
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is where the electrons reside an orbital
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should never be confused with an orbit
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an orbit is a mathematically defined
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pathway for example how the Earth orbits
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the Sun using classical Newtonian
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physics we can predict where the earth
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will be on the orbit at some time T and
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where it was at some time T in the past
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you may have seen a similar simplified
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model of the atom where the electron is
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orbiting the nucleus on a mathematically
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defined pathway which couldn't be
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further from the truth an orbital is a
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much more complicated concept than an
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orbit in fact we know nothing about how
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the electron moves around the nucleus
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thus quantum mechanics demonstrated that
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electrons did not move around in neat
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orbits but existed in regions called
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orbitals with a fixed amount of energy
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in simplest terms an orbital is a
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three-dimensional region or shape and
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you can expect to find an electron
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inside the shape 90% of the time and may
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help to think of the shape as a boundary
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surface the electron is more likely to
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be inside this boundary shape rather
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than outside the boundary let's apply
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this concept of boundary shape to the
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electron of the hydrogen atom which has
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one proton in the nucleus and one
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electron in a surrounding orbital if you
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imagine the electron is moving in a
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random manner with fixed energy around
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the nucleus and then imagine that we
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take a picture of this electron every
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second for a day a week or month we see
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that all these pictures laid on top of
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one
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begin to form an electron cloud around
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the nucleus remember all these
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hypothetical pictures or data points
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represent where the electron has been
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over time if we now attempt to create a
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three-dimensional surface to encompass
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90% of all these data points we obtain a
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sphere which is often called the
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boundary surface the creation of this
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boundary surface for the hydrogen atom
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which is called an S orbital requires
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some pretty complex calculus thus if an
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electron is in an orbital the electron
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has a fixed amount of energy and the
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orbital is a three-dimensional region
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around the nucleus that indicates the
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probable location of that electron 90%
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of the time there are many different
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orbitals for the electrons to reside the
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success of solutions or orbitals from
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quantum mechanics increase in relative
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energy when we add the shapes to the
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energy terms we get the following
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electron configuration diagram which
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shows all the orbitals available for
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electrons to reside the orbitals fall
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into one of four broad categories s P D
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and F orbitals interestingly there is
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one solution each time an S orbital is
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obtained three solutions of the same
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energy each time a P solution is
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obtained five solutions of the same
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energy each time a D solution is
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obtained and seven solutions of the same
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energy each time an F solution is
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obtained in the next chapter we will
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revisit this diagram in detail to aid in
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writing electron configurations for now
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let's just focus on what this diagram
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represents the orbitals and each of
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these lines abstractly represents an
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orbital for example the first line on
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the electron configuration diagram is
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the 1s orbital and it is a sphere this
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is where the first two electrons of an
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atom can be found 90% of the time
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in addition all the s orbitals are
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shaped like spheres the three 2p
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orbitals are shaped like dumbbells
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oriented along the three axis the 2px
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2py and 2pz for convenience your
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instructor will often shrink them down
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to a third of their size so that they
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are easier to draw if we continue to go
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up and relative energy the shapes of the
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orbitals become increasingly more
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complicated as demonstrated by the 3d
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orbital shapes and it is unlikely that
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your instructor will hold you
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accountable before these shapes although
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this diagram may look complicated
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remember that each line abstractly
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represents an orbital and that all these
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orbitals overlap on the same atom here
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you can see that a 1s orbital is the
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first orbital that the electrons will
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reside in then the 2's orbital is on top
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of that then the three 2p orbitals on
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top of them and so on and so on until
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the necessary amount of orbitals are
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present to house all of the electrons
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that an atom may possess if orbitals are
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where electrons can be found 90% of the
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time in the next chapter we will examine
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how many electrons are in each orbital
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and the order in which they are filled
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by an atom
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[Music]
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the arrangement of electrons in an atom
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is known as the atoms electron
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configuration think of this as finding a
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home for each electron electrons want to
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be in the lowest energy arrangement
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called the ground state electron
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configuration and to accomplish this we
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need to follow three basic rules the
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alcohol principle tells us the order the
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orbitals are filled Alf ball is a german
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word meaning to build up just like
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building a house we need to start at the
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bottom floor when that is completely
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finished we begin on the next floor thus
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electrons are added to the lowest energy
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orbital first and then we work our way
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up in relative energy this means that on
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the electron configuration diagram
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electrons are placed into the 1s orbital
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first then the 2s followed by the 2p 3s
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3p and so on and so on until the
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necessary amount of orbitals are filled
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to house all of the electrons that an
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atom may possess the next rule is called
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the Pauli exclusion principle which
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simply translates to only two electrons
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per orbital with opposite spin within
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the electron configuration diagram we
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will represent electrons as 1/2 arrows
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the first arrow is up and the second
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arrow is down remember that each line on
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this diagram abstractly represents an
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orbital and that each arrow represents
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an electron in that orbital below the
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diagram is the electron configuration
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notation which utilizes exponents to
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indicate the number of electrons within
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each orbital the third and last rule is
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called
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Poon's rule which states orbitals of
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equal energy are occupied by one
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electron before any orbital is occupied
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by a second electron now let's review
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these three basic rules the first
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electron goes into lowest energy orbital
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1s orbital which is the Aufbau rule the
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second electron goes into that same
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orbital with opposite spin the Pauli
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exclusion principle states we can only
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have two electrons per orbital thus the
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third electron goes into the next
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highest energy orbital the 2s the fourth
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electron also goes into the 2's orbital
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with opposite spin followed by the fifth
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electron filling one of the 2p orbitals
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hoon's rule states that the six electron
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will go into a different 2p orbital
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because we should fill the orbitals one
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at a time across an energy level before
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pairing electrons subsequent electrons
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are added following these three basic
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rules until the required amount of
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electrons are added to work this example
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problem we first need to consult the
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periodic table to ascertain how many
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electrons are in a neutral atom of
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carbon in the first chapter we learned
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how to quickly deduce the number of
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electrons and we will meet the skill now
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the atomic number of carbon is 6
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thus a neutral atom of carbon has 6
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electrons therefore this problem simply
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translates to finding a home for 6
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electrons following our three simple
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rules we place all six electrons into
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our diagram as shown start at the bottom
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working our way up two electrons per
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orbital with opposite spin and fill the
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orbitals one at a time across an energy
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level before pairing electrons
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in this example we have one more
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electron than the atomic number of
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fluorine
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thus examining the periodic table we see
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that fluorines atomic number is nine
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which means there are nine protons and
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ten electrons if we have a negative one
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charge thus the problem is really asking
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us to find a home for 10 electrons again
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following our three simple rules we
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place all 10 electrons into our diagram
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as shown in this example the calcium
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atom has lost two electrons when
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compared to the number of protons
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thus examining the periodic table we see
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that calcium so Tomic number is 20 which
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means there are 20 protons and 18
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electrons if we have a positive 2 charge
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thus the problem is really asking us to
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find a home for 18 electrons again
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following our three simple rules we
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place all 18 electrons into our diagram
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as shown
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[Music]
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first we need to consult the periodic
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table to ascertain how many electrons
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are in a neutral atom of gallium which
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will be the same as the atomic number
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for gallium gallium atomic number is 31
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which means there are 31 electrons if
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gallium has no charge thus the problem
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is really asking us to find a home for
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31 electrons again following our three
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simple rules we place all 31 electrons
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into our diagram as shown
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[Music]
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you are probably thinking that it is
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going to be very challenging to memorize
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and reproduce the electron configuration
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diagram template shown however if you
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have access to a periodic table you can
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easily reproduce it for example if you
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simply read the periodic table from left
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to right the correct order of orbital
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filling is obtained 1s 2s 2p 3s 3p 4s
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then you go down a level for the 3d back
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up to the 4p 5s down a level for the 4d
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and so on in addition the periodic table
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tells us how many electrons go into each
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sublevel for example the s block is 2
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elements across the Stu electrons can go
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into all the s sub levels the P block is
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6 elements across the 6 electrons can go
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in all the P sub levels the D block is
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10 elements across thus 10 electrons can
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go in all the D sub levels and finally
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the F block is 14 elements across which
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means 14 electrons can go in all the F
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sub levels you may notice that when we
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compare the order of filling we obtained
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from the periodic table to the electron
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configuration diagram template they are
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the same clearly having access to a
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periodic table helps us reproduce the
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electron configuration diagram template
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thus you should practice drawing this
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diagram on your own with the aid of a
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periodic table until you have mastered
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this skill
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as you can tell the keys to writing
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electron configurations are to quickly
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ascertain the number of electrons for an
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atom or ion from the periodic table and
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to be able to quickly reproduce the
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template for the electron configuration
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diagram remember you can use the
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periodic table to help you reproduce it
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then simply follow the three basic rules
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for electron configurations and you
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should have no problems determining
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electron configurations
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you
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English (auto-generated)