Review Chapter 5: Things to Know
o What he thought:
Properties of elements could be arranged in groups of three- called a triad- such
that when the property of the first element was added to the property of the third element in the triad, the average would
be the property of the second element of the triad
o Example of a Triad:
Be, Mg, Ca
o Why triads don’t’
work for elements over atomic number 20:
After atomic number 20, the number of protons and neutrons is no longer in a 1
to 1 ratio, so the atomic mass and the atomic number no longer correspond. At
Dobereiner’s time, atomic number was not known, so the triad idea was somewhat faulty.
o What he thought:
If elements are arranged in increasing atomic mass order, the physical and chemical
properties would repeat themselves every 8th element. He did not pay
attention to apparent discrepancies in properties as noted by the increase atomic number in the table without leaving spaces
for undiscovered elements.
o Why did elements repeat
every 8th (why was there no p6 column):
At Newlands time, many of the noble gasses had not been discovered. Most elements were being discovered by the reactions they underwent.
Since noble gasses are inert (non reactive), the noble gasses were not found until later times.
o By what did he arrange
Increasing atomic mass.
o Why did he not want
to arrange it exclusively by atomic mass?
He saw that if the elements were not arranged by mass, the properties of the elements
seemed to be more in line. Therefore, he broke the traditional ordering by number and changed it to a modified atomic mass order (knew that something else dictated
the order, just did not know what- turned out to be atomic number)
o What else did he do
that was a break from traditional thought?
He also left spaces for elements that were not yet discovered. He believed that if spaces were left, elements with properties that he had predicted would fill those spaces. That is why his table became so useful, because he showed the world that it could
be used to predict the properties of elements that had not yet been discovered.
o What is an example
of one of his exceptions
He thought the mass of argon had been erroneously calculated and must be redone,
for when argon and potassium were put out of mass order, the properties of the elements made more harmonious sense.
o What is an example
of his predictions
He predicted the existence of the elements that later had the properties of gallium,
germanium, and scandium.
o How did he explain
the exceptions Mendeleev noted in the table?
If elements were arranged in increasing atomic number order, the table as arranged
by Mendeleev would make sense. The exceptions to the mass order arose to the
fact that after element number twenty, the number of neutrons rose drastically and not in a steady pattern, such that the
mass of argon was actually more than the mass of potassium because it had more neutrons.
o What property did he
use to organize his table?
Atomic number- the number of protons in the nucleus.
o In his arrogance, what
did he win the Noble Prize for?
Removing some elements from the body of the periodic table and making the “f”
block elements- was able to predict the properties of the elements that had not been produced yet.
Periodic Table Organization:
Which blocks make up the Representative Elements?
o S and P blocks
Which block is the transition metal
o D block
Which block is the inner transition metal
o F block
What is the name of the IA, IIA, VIIA, and VIIIA families?
o IA- alkaline
o IIA- Alkaline earth
o VIIA- halogens
o VIIIA- noble gases
What is a family/ group
o The vertical columns
on the table (18 of them)
What is a period
o The horizontal rows
on the table (7 of them)
What are the three systems for labeling the periodic table?
o American system, European
system, IUPAC system
What are the seven semi- metals (metalloids)
o Boron, Silicon, Germanium,
Arsenic, Antimony, Tellurium, (sometimes considered Polonium), Astatine
Where are the metals found? Where are the non-metals found?
o Metals are found to
the left of the semimetals; non-metals are found to the right of the semimetals.
Definitions to know:
o Ionization energy
Energy to remove an electron from an element
o Electron affinity
Energy change as result of addition of an electron to an element
Value that indicates the desire of an element to gain an electron in a chemical
o Atomic radius
Distance from the center of the nucleus to the outside of an atom
o Ionic radius
Distance from the center of the nucleus to the outside of an ion
o Successive ionization
Energy required to remove successive electrons from an atom
o Second ionization energy
Energy required to remove the second electron from and atom
o Noble gas inner core
Electron configuration of an ion that is the same as the previous noble gas.
o Relative nuclear charge
Charge of the nucleus based on the number of electrons in the atom, responsible
for determining ionic radii and atomic radii
Be able to explain the trends in:
o Atomic radius (in which
direction does the atom get larger)
Moving from right to left and down increases atomic radius.
o Ionic radius (what
happens when an atom becomes a positive ion? A negative ion?
When at atom becomes a positive ion (loses an electron)- the radius becomes smaller-
the relative nuclear charge increases and often energy levels are lost
When an atom becomes a negative ion (gains an electron) – the radius becomes
larger- the relative nuclear charge decreases and the outermost electrons move further away from the nucleus.
o Ionization energy (in
which direction does ionization energy increase?)
Moving up and to the right the ionization energy increases (opposite atomic radius)
What happens to ionization energy when all the valence electrons have been removed?
Once all the valence electrons have been removed, there is a drastic jump in the
amount of energy needed to remove another electron from an atom. This is because
the ion has achieved a stable noble gas inner core electron configuration.
o Electron Affinity
Generally follows ionization energy
The negative sign means that energy is given off when the electron is added- means
it goes naturally- does not need to be forced on. The larger the negative value,
the more energy that is given off, the more the element desired the electron.
A positive value tends to mean the element did not desire another electron- energy
needed to be added to force another electron onto the atom. Noble gasses and
the s2 electrons tend to be positive values.
Generally follows both ionization energy and electron affinity
No units for electronegativity
Noble gasses have no electronegativity
Be able to predict which atoms would be larger or smaller values for any of the trends
Memorize 1-20 on the ion list.