Soon you’ll be able to explain everyday things, like why baking soda and vinegar bubble, why only certain chemicals grow crystals, what fire really is made of, how to transform copper into gold, and how to make cold light. Once you wrap your head around these basic chemistry ideas (like acids, polymers, and kinetics), you can make better choices about the products you use everyday like pain relievers, cold compresses, and getting a loaf of bread to rise. Are your ready? This video will get you started with your lesson in molecules:

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8 Responses to “Unit 8: Chemistry (Molecules) Video”

  1. Each molecule/atom has its own unique set of properties, including melting and freezing temperatures. Just because one atom, like hydrogen, is a gas at a temperature doesn’t dictate that a molecule that it’s a part of is a gas at that same temperature. Water has its own set of properties that don’t show up with just hydrogen, like water is a polar molecule (it has a plus and minus charge).

    On a more technical level, the bonds between the hydrogen and oxygen are covalent, which means that the electrons are shared, not transferred between each other), and that’s the force that holds the water molecule together. To turn into a gas, those bonds need to be broken, and at room temperature, there isn’t enough kinetic energy to break it into a gas, so the water stays liquid.

  2. Dear Aurora,
    If oxygen and hydrogen are both gases at 0 degrees Celsius (32 degrees Fahrenheit), why is water, which is made of oxygen and hydrogen, a solid at that temperature?
    Thanks for your help,
    Miss B.

  3. Ok – thanks! It should be fixed now. 🙂

  4. Hmmm.. where exactly are the links incorrect? We want to get this fixed ASAP. Which page are the links incorrect on?

  5. Mary Hackenberg says:

    I am finding the Lesson 1 and Lesson 2 videos in the wrong links. That is, they are reversed. When we click on Molecules, we get Chemical Kinetics, and vice versa.

  6. Ok – this is going to be a long answer, so bear with me…

    Electron Distribution around the atom has taken on new directions since the time of the electron buzzing around the nucleus like planets around the Sun. So get out your periodic table and follow along.

    Every element is composted of electrons(e), protons(p), and neutrons(n). The number of protons in the nucleus defines the element; it is the ATOMIC NUMBER. H has 1p, C has 6p, U has 92 protons. Neutrons also occupy the nucleus with the protons.

    Consider a single atom of C. One atom could have 6p and 6n. The atomic number is 6. The atomic MASS is 12, the sum of the p & n. Another atom of C could have 6p and 8n. The atomic mass is 14. These two atoms are ISOTOPES of carbon; same #p but different #n. Every element is composed of two or more isotopes. The distribution depends on their stability. For instance, carbon, is composed of C12, C13, and C14; but not 33.3% of each isotope. If we take the average mass of all of the isotopes, we usually get a number that is not an integer. This average mass is the ATOMIC WEIGHT. For carbon, it is 12.01, meaning most of the atoms are C-12 and very little C-13 and C-14.

    Okay, the periodic table is divided into rows (containing elements increasing in atomic number) and columns or families (containing elements with similar chemical behavior). There are 7 periods each representing a main energy level (MEL) occupied by electrons (the old “shell”). Each MEL is composed of a series of sublevels. Each sublevel is described by an ORBITAL; a region or volume in space that the electron will have the greatest possibility of occupying. We don’t use the orbit anymore; it is too confining so we speak of probabilities of finding an electron within one of these spaces/volumes. Each orbital can have a maximum of 2 e.

    The number of sublevels in a MEL is equal to the number of that MEL. So MEL 1 has 1 sublevel, MEL 2 has 2 sublevels and so on. Each sublevel is represented by a lower case letter. In order of increasing energy, they are s,p,d,f (smart people don’t flunk).

    The number of orbitals in a sublevel; s has 1, p has 3, d has 5, f has 7.

    So the 1st MEL has 1s sublevel and 2e max
    The 2nd MEL has a 2s sublevel (2e) and a 2p sublevel (6e) for a total of 8e
    The 3rd MEL has a 3s sublevel (2e), a 3p sublevel (6e), and a 3d sublevel (10e) for a total of 18e
    The 4th MEL has a 4s (2e), 4p (6e), 4d(10e), and 4f(14e) totaling 32e

    There are only 4 sublevels even thought there are 7 MEL.

    Now we begin to fill the MELs and sublevels. This is where it gets tricky. First, electrons always enter the orbitals of lowest possible energy.

    Now look at the periodic table. The first 2 columns (headed by H and Be) are elements where the last electrons entering the atom occupy s orbitals. In fact you could draw a bracket above the first 2 columns and label it “s orbitals”. All of the elements under H and Be (Li, Na, Mg, etc are elements where the last electron that entered went into a s sublevel. H has 1 e in the 1st MEL, the 1s sublevel. Li and Be have electrons in the 2s sublevel. Na and Mg have electrons in the 3s sublevel, etc all the way down to Fr and Ra with electrons in the 7s sublevel.

    Now go over to the right side of the table and look at the columns headed B thru Ne, The elements in these columns are called the Representative Elements. Count up the number of columns. 1 thru 6. All of the last electrons entering these elements are entering the p sublevels. Remember the p sublevel has 3 orbitals and 2 e per orbital means 6 electrons total. B thru Ne has the last electron entering the 2p sublevel. Al thru Ar has the last electrons entering the 3p sublevel, etc, down to Tl thru Rn with electron entering the …count down…the 6p level.

    IN the middle now, and it get a bit confusing at first. Remember, electrons always enter the orbitals of lowest possible energy first. Okay. Find the series of elements Sc thru Zn. The last electrons entering these go into the 3d level (NOT the 4d level. We haven’t filled the 3d level yet. But the 3d level is in the 4th MEL). The last electron entering Y thru Cd enter the 4d level, and so on. These are the Transition Metals.

    Go to the bottom of the table and see 2 separate rows. The first with La thru Lu have last electrons entering the 4f siublevel, and Ac thru Lr, the 5f sublevel. These are the Rare Earth Elements.

    Now lets write the ELECTRON CONFIGURATION for a series of elements so you can see how and where the electrons are going. There is a symbolism here.

    1s1 (below I’ll write this as 1s1 but the last number is always a superscript) means electrons are entering the 1st MEL, into the 1s sublevel, and the superscript indicates the number of electron in that sublevel. This is the electron configuration for H. Let’s try oxygen. Electrons are added left to right and top to bottom as you proceed across the periodic table. So oxygen would be

    O: 1s2 2s2 2p4 .Sum the superscripts to give the total # e in the atom. For a neutral atom, this number will also be the number of protons or the atomic number

    Ne would be

    Ne: 1s2 2s2 2p6

    Now we have filled both the 1st and 2nd MEL so we start again with the 3s. Try doing Cl and check your answer.

    Cl: 1s2 2s2 2p6 3s2 3p5

    Okay, the 3rd MEL has 3 sublevels, s, p, d. They fill in this order, but ELECTRONS ALWAYS FILL THE ORBITALS WITH THE LOWEST POSSIBLE ENERGY. (did I mention this already?) So here’s what happens next. After filling Ar with the 3p6, we say that we have filled everything up to Ar so we can put Ar in brackets [Ar], indicating all’s full up to here. Next element is K.

    K; [Ar] 4s1 and then

    Ca: {Ar] 4s2 because THE 4s SUBLEVEL HAS ALOWER ENERGY THAN THE 3d so electrons enter there first. THEN the 3d sublevel is filled. So

    Ni: [Ar] 4s2 3d8 would be the electron configuration for nickel. So following this system try Ag, silver, without peeking. Do the whole thing from H.

    Ag: 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d9

    So that’s about it for electrons in there “shells”. If this is too obtuse, I’ll try to help again. Maybe after reading this try the general chemistry text again.

    Hope this hasn’t been too confusing. Let me know.

  7. Dear Aurora,

    HELP! But first, like so many others before me, Thank you so much for such a great program. I am using the Silver Mastery Program along with e-science and it has been great. We have done all of the experiments on Air Pressure ( they all turned out beautifully!). We have made pop rockets ( higher than the building we were in), we have completed our basic circuits, made our jigglebot and are completing our racerbot this week. Had trouble finding soap dishes for our remote, and ended up using old boxes that hold checks ( to hold our batteries and switches). They worked just fine. We also learned how to make “tumblewings” and “hand gliders” ( from a web site you gave us). After a couple of weeks of trial and error, they have become expert “fliers”.
    We are now preparing to put on a “show”-demonstration in three weeks to share all we have done with other kids, friends, grandparents etc. We are just beginning Unit 3 on Matter.
    So… I know my question will sound feel free to shake your head turn off your computer :>)
    Here goes: The Periodic Table…I have to admit I haven’t looked at one since College Chemistry ( say over 40 years ago…)
    I have read over and over the materials from e-science about the electron shells. From your materials ” An atom can have as few as one and as many as seven shells.” So far so good. I understand the equation 2n2 ( how many electrons can be in each shell) .
    Looking at the Periodic table I also understand that the number in the upper left corner is the Atomic number ( number of protons) which also tell me the number of electrons ( right??)
    The number in the lower right hand corner is the Atomic weight. I remember that you subtract the Atomic number from the weight to get the number of neutrons.
    So far so good…right??

    Here’s my problem…question…For example: If I use the mathematical formula for say Ti ( titanium) I would have 22 protons and 26 neutrons. Then I would have 2 electrons in the 1st shell, 8 electrons in the 2nd shell and 12 electrons in the 3rd shell ( which could hold 18 to be full right ??) My calculation shows that Ti has 3 shells.

    Then I remembered ( from that old Chemistry class) that the rows and the columns told me something. Yikes! So I looked in an old chemistry book and it said ” The atoms of all the elements in the same row ( or period) contain the same number of atomic shells. It said ” the periods are numbered 1-7 indicating the number of shells that the elements in that period contain. THEN it said ” The atoms of all the elements in the same column ( or group) contain the same number of outer-shell electrons.

    So… does that mean that for example “Row 4” ( on the table) K Ca Sc Ti V Cr etc. all contain the same number of shells? With the formula I can’t make that work.

    K to Ni would have 3 shells, but then Zn etc. in that row would have 4 shells. Am I really confused??? I don’t want to confuse the kids, but they seem to know ( from some other teacher) that the row numbers and columns “mean” something.

    I don’t know if you will be able to explain (in a comment box), but if you gave me some examples of different elements and the number of shells etc. I think I could figure it out. I really like the way you explain things !!

    Thanks for listening.