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Chemistry

Reveiw Chapter 5
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Review Chapter 5:  Things to Know

 

Basic Information about:

 

-         Dobereiner:

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.

 

-         Newlands:

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 his table?

         Increasing atomic mass.

 

-         Mendeleev:

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.

 

-         Mosely:

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.

 

-         Seaborg:

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

o       Electronegativity

         Value that indicates the desire of an element to gain an electron in a chemical bond.

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

         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.

 

o       Electronegativity

         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.