Tuesday, December 11, 2007
Tues-Day 2
Bio- HW due THURSDAY is to outline text Section 34.1
We began our new unit on the Integumentary (Skin) System, Musculatory (Muscles) System, and the Skeletal (Bones) System.
Often, we will discuss an organism's structures and their functions in terms of evolution i.e. how a structure can be an adaptation, which is a trait that enhances a species' chances of survival in the environment. One student had a question about the rate of human evolution and, how timely, an article was published TODAY on just that question!
Here is the article.
Later in our course, you will be able to understand that article in more detail.
We began by looking at a cross section of the skin showing the different layers and types of cells that make up the ORGAN, the skin. In fact, the skin is the LARGEST organ of the human body.
We emphasized the structure and FUNCTIONS of each layer of cells:
the epidermis has a layer of KERATIN-containing dead cells that protect you from bacteria, chemicals, and heat. The BASAL cells are just underneath the dead cell layer and contain the dark pigment, MELANIN, which absorbs harmful UV rays/photons to protect against cell mutations.
The main layer of skin, the DERMIS, is underneath the epidermis and contains hair follicle cells surrounded by oil/sebaceous glands, various neurons/nerve cells, sweat glands that lead up to pores at the top of the epidermis, muscle fibers, and blood vessels. The dermis functions in regulation/homeostasis by responding to the environment via its nerve cells, muscle fibers, and sweat glands (thermo-regulation/heat regulation via sweating).
There is a layer of fat cells beneath the dermis to provide insulation, protection, and energy.
Chem 7/8- we reviewed characteristics of metals and nonmetals and saw some examples of each.
We then introduced the TWO most important factors in determining the chemical properties of an element via the attraction of the nucleus for its valence electrons.
The first factor is Zeff (EFFECTIVE/NET NUCLEAR CHARGE) on the valence electrons. This is calculated by taking the number of protons in the nucleus (the nuclear charge, Z) and subtracting the number of SHIELDING/BLOCKING/KERNEL/INNER P.E.L. electrons. That number is the NET positive charge that is attracting the valence electron to the nucleus.
The greater the Zeff on a valence electron, the stronger its attraction to the nucleus!
The other factor is 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, theFARTHER 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 will apply this information to each periodic trend to see how these factors affect each property of elements.
Chem 9- we reviewed characteristics of metals and nonmetals and saw some examples of each.
We then introduced the TWO most important factors in determining the chemical properties of an element via the attraction of the nucleus for its valence electrons.
The first factor is Zeff (EFFECTIVE/NET NUCLEAR CHARGE) on the valence electrons. This is calculated by taking the number of protons in the nucleus (the nuclear charge, Z) and subtracting the number of SHIELDING/BLOCKING/KERNEL/INNER P.E.L. electrons. That number is the NET positive charge that is attracting the valence electron to the nucleus.
The greater the Zeff on a valence electron, the stronger its attraction to the nucleus!
The other factor is 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, theFARTHER away the electron, the LESSER the attraction on that electron from the nucleus.
Tomorrow, we will work out some examples and apply this information.
We began our new unit on the Integumentary (Skin) System, Musculatory (Muscles) System, and the Skeletal (Bones) System.
Often, we will discuss an organism's structures and their functions in terms of evolution i.e. how a structure can be an adaptation, which is a trait that enhances a species' chances of survival in the environment. One student had a question about the rate of human evolution and, how timely, an article was published TODAY on just that question!
Here is the article.
Later in our course, you will be able to understand that article in more detail.
We began by looking at a cross section of the skin showing the different layers and types of cells that make up the ORGAN, the skin. In fact, the skin is the LARGEST organ of the human body.
We emphasized the structure and FUNCTIONS of each layer of cells:
the epidermis has a layer of KERATIN-containing dead cells that protect you from bacteria, chemicals, and heat. The BASAL cells are just underneath the dead cell layer and contain the dark pigment, MELANIN, which absorbs harmful UV rays/photons to protect against cell mutations.
The main layer of skin, the DERMIS, is underneath the epidermis and contains hair follicle cells surrounded by oil/sebaceous glands, various neurons/nerve cells, sweat glands that lead up to pores at the top of the epidermis, muscle fibers, and blood vessels. The dermis functions in regulation/homeostasis by responding to the environment via its nerve cells, muscle fibers, and sweat glands (thermo-regulation/heat regulation via sweating).
There is a layer of fat cells beneath the dermis to provide insulation, protection, and energy.
Chem 7/8- we reviewed characteristics of metals and nonmetals and saw some examples of each.
We then introduced the TWO most important factors in determining the chemical properties of an element via the attraction of the nucleus for its valence electrons.
The first factor is Zeff (EFFECTIVE/NET NUCLEAR CHARGE) on the valence electrons. This is calculated by taking the number of protons in the nucleus (the nuclear charge, Z) and subtracting the number of SHIELDING/BLOCKING/KERNEL/INNER P.E.L. electrons. That number is the NET positive charge that is attracting the valence electron to the nucleus.
The greater the Zeff on a valence electron, the stronger its attraction to the nucleus!
The other factor is 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, theFARTHER 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 will apply this information to each periodic trend to see how these factors affect each property of elements.
Chem 9- we reviewed characteristics of metals and nonmetals and saw some examples of each.
We then introduced the TWO most important factors in determining the chemical properties of an element via the attraction of the nucleus for its valence electrons.
The first factor is Zeff (EFFECTIVE/NET NUCLEAR CHARGE) on the valence electrons. This is calculated by taking the number of protons in the nucleus (the nuclear charge, Z) and subtracting the number of SHIELDING/BLOCKING/KERNEL/INNER P.E.L. electrons. That number is the NET positive charge that is attracting the valence electron to the nucleus.
The greater the Zeff on a valence electron, the stronger its attraction to the nucleus!
The other factor is 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, theFARTHER away the electron, the LESSER the attraction on that electron from the nucleus.
Tomorrow, we will work out some examples and apply this information.
# posted by C @ 11:50 AM 
