Wednesday, December 12, 2007
Wednes-Day 1
Bio- Reminder: for hw, outline text section 34.1
we reviewed the structures and functions of the skin and then we discussed the immune system process that occurs when skin is cut into the dermis layer. Overall, the skin has many functions and works cooperatively with many other organ systems (circulatory, immune, etc.) in the body.
We reviewed our test on cellular respiration and photosynthesis, noting some of the test skills that would have improved your test scores and made the test easier to answer.
In general, more students could take advantage of the diagrams and pictures from the part I section to help them on the part II section of the test.
We then began to talk about the life process of LOCOMOTION, which involves the musculo-skeletal system of the body.
Chem 7- we continued our discussion of Zeff and OPEL's seeing that ACROSS A PERIOD (left to right) Zeff on the valence electrons increases but the number of OPEL's remains the same; that results in an increasing attraction for valence electrons as you go from the metals to the nonmetals. That is why nonmetals have a higher first ionization energy and a higher electronegativity than metals in a given period. It is also the reason that the nonmetal atoms are smaller than the metal atoms in a given period because the nonmetal electrons are drawn in closer due to the higher Zeff from the nonmetal nucleus.
When considered DOWN A GROUP/FAMILY, the Zeff on the valence electrons remains the SAME but the number of OPEL's INCREASES. Therefore, as you go down a group, the valence electrons are farther and farther away from the nucleus and thus experience less attraction to the nucleus. So, the first ionization energy and the electronegativity decreases down a group but the atomic radius INCREASES down a group.
We will apply Zeff and OPEL's to explain chemistry for the REST OF THE YEAR so it important to draw out and understand how those two factors determine the strength of attraction between the nucleus and the valence electrons.
Chem 8/9- We review Zeff, the effective nuclear charge on an electron; the greater the Zeff on an electron, the stronger it is attracted to the nucleus.
We then looked at the second factor that determines how strongly an atom's nucleus attracts its valence electrons; that factor is the DISTANCE between the nucleus (+) and the electron. The closer the electron is to the nucleus, the stronger the attraction between these oppositely charged particles. How far away, on average, the valence electron is from the nucleus as indicated by the PRINCIPAL ENERGY LEVEL NUMBER of the valence electron, which equals the total number of OCCUPIED PRINCIPAL ENERGY LEVELS (OPEL's).
The higher the P.E.L. number of the electron, the FARTHER away the electron, the LESSER the attraction on that electron from the nucleus.
We saw that, as you go from left to right across a period, Zeff increases (on the valence electrons) and the number of OPEL's STAYS THE SAME causing a greater attraction on the valence electrons of each increasing atomic number element. SO, metals have a weak attraction for their valence electrons and nonmetals have a strong attraction for their valence electrons.
Down a GROUP, the Zeff on the valence electron(s) STAYS THE SAME, but the number of OPEL's increases so the higher atomic number elements in a groups have a LESSER attraction for their valence electrons, which are farther and farther from the nucleus.
We continued our discussion of Zeff and OPEL's seeing that ACROSS A PERIOD (left to right) Zeff on the valence electrons increases but the number of OPEL's remains the same; that results in an increasing attraction for valence electrons as you go from the metals to the nonmetals. That is why nonmetals have a higher first ionization energy and a higher electronegativity than metals in a given period. It is also the reason that the nonmetal atoms are smaller than the metal atoms in a given period because the nonmetal electrons are drawn in closer due to the higher Zeff from the nonmetal nucleus.
When considered DOWN A GROUP/FAMILY, the Zeff on the valence electrons remains the SAME but the number of OPEL's INCREASES. Therefore, as you go down a group, the valence electrons are farther and farther away from the nucleus and thus experience less attraction to the nucleus. So, the first ionization energy and the electronegativity decreases down a group but the atomic radius INCREASES down a group.
We will apply Zeff and OPEL's to explain chemistry for the REST OF THE YEAR so it important to draw out and understand how those two factors determine the strength of attraction between the nucleus and the valence electrons.
We then did an activity in which we looked at various properties of elements and deciphered the location of the elements on a periodic table.
we reviewed the structures and functions of the skin and then we discussed the immune system process that occurs when skin is cut into the dermis layer. Overall, the skin has many functions and works cooperatively with many other organ systems (circulatory, immune, etc.) in the body.
We reviewed our test on cellular respiration and photosynthesis, noting some of the test skills that would have improved your test scores and made the test easier to answer.
In general, more students could take advantage of the diagrams and pictures from the part I section to help them on the part II section of the test.
We then began to talk about the life process of LOCOMOTION, which involves the musculo-skeletal system of the body.
Chem 7- we continued our discussion of Zeff and OPEL's seeing that ACROSS A PERIOD (left to right) Zeff on the valence electrons increases but the number of OPEL's remains the same; that results in an increasing attraction for valence electrons as you go from the metals to the nonmetals. That is why nonmetals have a higher first ionization energy and a higher electronegativity than metals in a given period. It is also the reason that the nonmetal atoms are smaller than the metal atoms in a given period because the nonmetal electrons are drawn in closer due to the higher Zeff from the nonmetal nucleus.
When considered DOWN A GROUP/FAMILY, the Zeff on the valence electrons remains the SAME but the number of OPEL's INCREASES. Therefore, as you go down a group, the valence electrons are farther and farther away from the nucleus and thus experience less attraction to the nucleus. So, the first ionization energy and the electronegativity decreases down a group but the atomic radius INCREASES down a group.
We will apply Zeff and OPEL's to explain chemistry for the REST OF THE YEAR so it important to draw out and understand how those two factors determine the strength of attraction between the nucleus and the valence electrons.
Chem 8/9- We review Zeff, the effective nuclear charge on an electron; the greater the Zeff on an electron, the stronger it is attracted to the nucleus.
We then looked at the second factor that determines how strongly an atom's nucleus attracts its valence electrons; that factor is the DISTANCE between the nucleus (+) and the electron. The closer the electron is to the nucleus, the stronger the attraction between these oppositely charged particles. How far away, on average, the valence electron is from the nucleus as indicated by the PRINCIPAL ENERGY LEVEL NUMBER of the valence electron, which equals the total number of OCCUPIED PRINCIPAL ENERGY LEVELS (OPEL's).
The higher the P.E.L. number of the electron, the FARTHER away the electron, the LESSER the attraction on that electron from the nucleus.
We saw that, as you go from left to right across a period, Zeff increases (on the valence electrons) and the number of OPEL's STAYS THE SAME causing a greater attraction on the valence electrons of each increasing atomic number element. SO, metals have a weak attraction for their valence electrons and nonmetals have a strong attraction for their valence electrons.
Down a GROUP, the Zeff on the valence electron(s) STAYS THE SAME, but the number of OPEL's increases so the higher atomic number elements in a groups have a LESSER attraction for their valence electrons, which are farther and farther from the nucleus.
We continued our discussion of Zeff and OPEL's seeing that ACROSS A PERIOD (left to right) Zeff on the valence electrons increases but the number of OPEL's remains the same; that results in an increasing attraction for valence electrons as you go from the metals to the nonmetals. That is why nonmetals have a higher first ionization energy and a higher electronegativity than metals in a given period. It is also the reason that the nonmetal atoms are smaller than the metal atoms in a given period because the nonmetal electrons are drawn in closer due to the higher Zeff from the nonmetal nucleus.
When considered DOWN A GROUP/FAMILY, the Zeff on the valence electrons remains the SAME but the number of OPEL's INCREASES. Therefore, as you go down a group, the valence electrons are farther and farther away from the nucleus and thus experience less attraction to the nucleus. So, the first ionization energy and the electronegativity decreases down a group but the atomic radius INCREASES down a group.
We will apply Zeff and OPEL's to explain chemistry for the REST OF THE YEAR so it important to draw out and understand how those two factors determine the strength of attraction between the nucleus and the valence electrons.
We then did an activity in which we looked at various properties of elements and deciphered the location of the elements on a periodic table.
# posted by C @ 4:01 PM 
