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Acid is any compound that forms a H+ ions in a solution.

Base a compound that produces OH- ions in solutions.

Ph Scale measurement system of the H+ ions in solutions.

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Weak acids or bases that can react with strong acids or bases to prevent sharp sudden changes in Ph.

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All the components of a solution are evenly distributed throughout the solution.

Suspension- non dissolved material that can settle

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Multiple hydrogen bonds between water molecules is that it takes a large amount of heat energy to cause those molecules to move faster.

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Cohesion is the attraction of molecules of the same substance.

Adhesion is the attraction of molecules of different substances.

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A special type of Dipole-Dipole attractive force is Hydrogen Bonding . This type of bonding occurs when a hydrogen atom is bonded to an oxygen, nitrogen, or fluorine atom. This attraction...

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The attraction between a hydrogen atom with a partial positive charge and and another atom with a partial negative charge.

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The gecko's amazing ability to stick to surfaces and walk up walls has inspired many researchers to manufacture materials that mimic the special surface of a gecko's foot. The secret behind the gecko's ability to stick so well is a forest of pillars at the micro-/nano-scale on the underside of the gecko's foot. Because there are so many pillars so close together, they are held tightly to the surface the gecko is walking on by a molecular force called the Van der Waals force. This relatively weak force causes uncharged molecules to attract each other.

In an unprecedented feat, Liming Dai, at the University of Dayton, and colleagues report in the October 10th issue of Science successful construction of a gecko-inspired adhesive that is ten times stronger than a gecko, at about 100 newtons per square centimeter.

The researchers constructed their adhesive out of two slightly different layers of multi-walled carbon nanotubes. The lower layer is composed of vertically-aligned carbon nanotubes, while the upper segment-which comes into contact with the surface it is sticking to-is curly, like a mess of spaghetti.

As shown in the figure, the adhesive sticks best when it is pulled down parallel to the surface it is sticking to-this is called shear adhesion. This action arranges the tips of the curly nanotubes so they have maximum contact with the substrate, thereby maximizing the Van der Waals force. Pulling the adhesive off in a motion perpendicular to the substrate is much easier-at this angle the sticking force is ten times weaker.

In this way, the adhesive has strong shear adhesion for firm attachment and relatively weak adhesion for detachment perpendicularly to the substrate. Just like a gecko, the adhesive can stick to a wall when needed, and then lift off easily to take the next step. This breakthrough, supported by the National Science Foundation, will have many technological applications.

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Scientists Copy Gecko Feet For Super Glue

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The gecko's amazing ability to stick to surfaces and walk up walls has inspired many researchers to manufacture materials that mimic the special surface of a gecko's foot. The secret behind the gecko's ability to stick so well is a forest of pillars at the micro-/nano-scale on the underside of the gecko's foot.

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When molecules are close together a slight attraction can develop between oppositly charged regions of nearby molecules.

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The world around us is made up of tiny units of matter called atoms. How these atoms stick together to form substances is called chemical bonding.

About Atoms

Each element has its own unique atom made up of a specific number of protons in its nucleus called the atomic number. Each atom also has the same number of electrons as it has protons.

Electron Shells

The electrons orbit around the nucleus of the atom. They stay in layers called shells. Each shell can only contain a certain number of electrons: the first layer can hold two electrons, the second layer eight electrons, the third layer eighteen electrons, etc.

The Outer Shell

All atoms would like to have a full outer shell, but the only elements to naturally have a full outer shell are the noble gases to the right of the periodic table. As a result, when atoms without full outer shells come into contact with other atoms, they tend to want to give up or gain electrons.

Valence Electrons

The valence electrons are the number of electrons an atom must lose or gain to have a full outer shell.

Atoms with a relatively empty outer shell will want to give up electrons. For example, if an atom has 1 electron out of a possible 8 in its outer shell, it will want to give up that electron so its outer shell is now full.

Atoms with a relatively full outer shell will want to gain electrons to fill up the outer shell. For example, an atom with 6 of 8 electrons in its outer shell will try to gain 2 electrons so its outer shell is full.

Ionic Bonding

Ionic bonding occurs when different elements trade electrons such that both elements now have a full outer shell.

Example:

Here is an example showing lithium (which has 3 electrons and 1 in the outer shell) and fluorine (which has 9 electrons and 7 in the outer shell) trading an electron to form LiF or lithium fluoride. This is called an ionic bond.

Example of ionic bonding

In covalent bonding electrons are shared between atoms rather than traded in order for the atoms of both elements to gain full outer shells. Electrons are always shared in pairs.

Example:

An example of covalent bonding is the molecule of carbon dioxide. In this example carbon has 4 of 8 electrons in its outer shell and oxygen has 6 of eight electrons. By combining two oxygen atoms with one carbon atom, the atoms can share electrons such that each atom has a full outer shell.

Example of covalent bonding

Interesting Facts about Chemical bonding

Because noble gases have a naturally full outer shell they seldom react.

In metallic bonding a large number of atoms lose their electrons.

Ionic bonding is mostly formed between metals located at the left side of the periodic table.

Atoms in molecules are held together by the attraction between the nucleus and the shared electrons.

More Chemistry Subjects

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The world around us is made up of tiny units of matter called atoms. How these atoms stick together to form substances is called chemical bonding. About Atoms Each element has its own unique atom made up of a specific number of protons in its nucleus called the atomic number.

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A chemical compound is a substance formed by the chemical combination of two or ore elements in definite proportions.

There are two types of chemical bonds they are ionic bonds and covalent bonds.

Ionic bonds are formed when 1 or more electrons are transferred from one atom to another.

Covalent bonds are when they share instead of transferring.

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For the better part of the past three decades, stable isotope geochemistry has become an increasingly common tool vertebrate paleontologists use to find out more about the biology and ecology of extinct organisms. The diet and ecology of an animal can often remain elusive when fossils are merely examined morphologically. Luckily, stable isotopes can tell us specific characteristics about what an animal is eating and the environments it lives in during its lifetime. Despite the fact this method is commonly used these days, there is a lot of background and jargon associated with it that many paleontologists have not been exposed to. In my two part series I am going to describe the foundations of these methods as they apply to paleontology, and then in part two I will highlight some recent work that illustrates how geochemical methods should be seen as an indispensible tool for paleontologists. Hopefully this brief description will help the method of stable isotope ecology become more accessible to all types of paleontologists!
What is an isotope?
Some elements have multiple stable forms with a different number of neutrons in the nucleus, known as isotopes. For example, a normal carbon atom has 6 protons and 6 neutrons in its nucleus, for an atomic weight of 12, but there is also a less abundant form of carbon that exists with an atomic weight of 13, meaning there are 6 protons and 7 neutrons in its nucleus. Heavier stable isotopes tend to be more rare on earth. The differing physical properties of isotopes of the same element lead to a predictable and often times systematic variation in the ratio of heavy to light isotopes in organic materials.
How are they measured?
Stable isotope ratios are measured using a isotope ratio mass spectrometer (IRMS). The basic mass spectrometer design has not been greatly modified since its invention by Alfred Nier in the 1940s while working on the Manhattan Project, hence the design is still called "Nier-type" today. A Nier-type IRMS is constructed of a source, flight tube, magnet, and collector cups. At the source, the sample gas is ionized and then accelerated into the flight tube. A giant magnet deflects the sample based on mass into collection cups, known as Faraday collectors. This collection creates an electrical current that is measured by a connected computer and converted into an isotope ratio. Samples are measured relative to a standard in "per mil" notation. Unknown samples are measured against known standards, which in the case of carbonates is Vienna Pee Dee Belemnite or V-PBD.
Isotopes in the environment
As bones, teeth, and eggshells mineralize, stable isotopic signatures from the water and food an organism is consuming will be locked in and recorded. Once mineralized, this signature will not change over the life of an animal. When we find a fossil, it is possible to measure these ratios using an IRMS, as previously mentioned, but what do they tell us about the environment specifically?

Perhaps on of the most useful stable isotope systems to understand for paleoecologists is the pattern of carbon isotopic fractionation in plants. Due to a physical isotope fractionation, C3 type plants preferentially fix ¹²C bearing Co ₂ during photosynthesis, resulting in δ ¹³C values that are strongly discriminated from the δ ¹³C of the atmosphere (currently ~-7‰), ranging between -35 and -25‰ depending on climate and ecology. In contrast, C4 plants have δ ¹³C values worldwide between -15 and -11‰. C3 and C4 plants tend to grow under different climate regimes, and this clear delineation in δ ¹³ C values of these plants provides a way to track changes in ecosystems and understand dynamics of environments in deep time.

Similar predictable fractionations occur with water in the environment and water in the body of an organism, which allows oxygen isotope ratios, δ ¹⁸O, to be useful for reconstructing the type of water the organism was drinking in their environment, for example, if it was highly evaporated or not. Oxygen isotope ratios recorded in tooth enamel are related to the drinking water of the organism, which is obtained from the environment. The δ ¹⁸O of environmental water is determined by the δ ¹⁸O of precipitation, which in turn is determined by temperature, evaporation, and the source of the precipitation air mass (Dansgaard 1964). Lighter isotopes of oxygen evaporate while heavier ones condense, meaning the greater the distance between the ocean and the air mass, rain will be lighter because heavy isotopes rainout preferentially earlier in travel of the air mass. Enrichment of δ ¹⁸O is greatest under arid, hot conditions. These systematic variations in the enrichment and fractionation of oxygen isotopes allows us to glean environmental information from the δ ¹⁸ O contained in fossil tooth enamel.

As you can see, there is a lot that can be described surrounding stable isotope ratios in fossils. I have only touched on carbon and oxygen, which are the two most commonly used in vertebrate paleontology isotopic studies, but I will be sure to highlight others in part two of this series where I will dive more into the applications of this method in recent case studies.

Additional reading:

Dansgaard, Willi. 1964. Stable isotopes in precipitation. Tellus 16 (4): 436-468.

Koch, Paul. 2007. Isotopic study of the biology of modern and fossil vertebrates. In Stable Isotopes in Ecology and Environmental Science. 2nd ed. Boston: Blackwell Publishing.

Sulzman, E W. 2007. Stable isotope chemistry and measurement: A primer. Stable Isotopes in Ecology and Environmental Science 1-21.

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Stable Isotopes in Ecology and Environmental Science

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So You Wanna Be a Paleoecologist? | The Integrative Paleontologists

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For the better part of the past three decades, stable isotope geochemistry has become an increasingly common tool vertebrate paleontologists use to find out more about the biology and ecology of extinct organisms. The diet and ecology of an animal can often remain elusive when fossils are merely examined morphologically.

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Isotopes have a larger amount of neutrons.

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Looking at another box from the Periodic Table we see the name of the element. This one is carbon. Its symbol is C. Its atomic number is 6.

As we noted in the last Project, the atomic number is the number of protons that an element has in its nucleus. Carbon has 6. If one is taken away leaving five, the atom is no longer a carbon atom but a boron atom. If a proton is added making seven, the atom becomes a nitrogen atom. Therefore, the number of protons in an atom must stay the same.

Although we can not do the Project to show it, protons have a positive charge. That means a carbon atom has six positive charges in the nucleus. Since an atom itself has no charge, six positive charges must be balanced by six negative charges or electrons. Changing the number of electrons changes the atom's charge but not its identity. Why?

That brings us to the neutrons. These have no charge but are almost the same size as the protons. Scientists did show this but in a type of Project we can not do. Since changing the number of neutrons does not change the identity of the atom [Why not?] or change the charge of the atom [Why not?], do all atoms of one element have the same number of neutrons?

The answer is no.

Scientists used a machine called a centrifuge to prove this. Perhaps you have gone to a carnival and ridden on a ride with a huge basket that spins around and around. While it is spinning, you are pressed against the basket and cannot move away from it. This is a people-sized centrifuge.

If a sample of an element is put into a laboratory-sized centrifuge and spun around and around, the heaviest atoms move to the outside and the lightest ones to the inside. You can do this yourself with a mixture of sand and gravel. Since you probably don't have a centrifuge handy, shake the mixture. The sand and gravel separate by size.

We now come to that last number in the element box: the atomic mass. If you look at all the elements, the atomic masses are not whole numbers. They have decimal parts. Why?

This Project on Candium will help show you why.

Candium is a special element we will make up just for this Project. I made mine out of chocolate covered peanuts, M&Ms and TicTacs. Another way is to use Peanut M&Ms, Skittles and Reese's Pieces.

If you do not or can not eat candy, you can use a different made up element called veggium. You can use dry peas, small dry beans and lentils. The Procedure is the same.

Question: What is the atomic mass of Candium?
Materials:
Scale

3 Clean custard cups

Sample of Candium

Bowl

Plate
Procedure:
Mix up some Candium. How to make Candium: Use a small mixing bowl from the kitchen. Put in two big handfuls of regular M&Ms, a handful of peanut M&Ms and a handful of Reese's Pieces. Mix these together. This is for a small batch for only you to do the Project. Increase the amounts if you need more candium but mix the entire batch you will need before beginning the Project.

Get a sample of Candium. For your sample, fill the custard cup but not so it will spill.

Note: DO NOT EAT ANY OF YOUR SAMPLE UNTIL AFTER YOU ARE DONE!

Pour the sample out onto the plate.

Mass a custard cup.

Sort out and count all of one kind of candy putting it into the custard cup.

Mass the candy in the custard cup.

Mass a second custard cup.

Sort out and count a second kind of candy putting it into this custard cup.

Mass the candy in the custard cup.

Mass the third custard cup.

Count the rest of the candy as you put it in this custard cup.

Mass the candy in the custard cup.
Analysis:
Calculate the masses of each kind of candy by subtracting the masses of the empty custard cups from the masses of the candy in the cups.

Add up the numbers of each kind of candy to find the total number of pieces of candy.

Calculate the average atomic mass of each kind of candy by dividing its mass by the number of pieces of that kind.

Calculate the relative abundance of each kind of candy by dividing the number of pieces of that kind by the total number of candium pieces.

Calculate the relative mass of each kind of candy in candium by multiplying the average mass of that kind by the relative abundance.

Add up the relative masses to get the atomic mass of candium.
Conclusions:
If you got a second sample of candium and did the Project a second time, do you think you would get the same atomic mass? Why do you think this?

If you did this Project using two samples twice as large, do you think they would give you the same atomic masses? Why do you think this?

What do you think the sum of the relative abundances would be? Add them up and find out if your prediction is correct.

Why would the sum be this number?
What I Found Out:
I mixed up a batch of candium. It smelled good.

The first kind of candy were the chocolate covered peanuts. There were 10 of them with a mass of 18.99g.

The second kind were orange TicTacs. There were 17 of them with a mass of 8.35g.

The third kind were the M&Ms. There were 33 of them with a mass of 29.50g.

There were a total of 10 + 17 + 33 or 60 pieces in my candium sample.

When I calculated the average atomic masses of each kind of candy, the first was 18.99g divided by 10 or 1.90g. The second kind was 8.35g divided by 17 or o.49g. The third kind was 29.50g divided by 33 or 0.89g.

The relative abundance of the first kind was 10 divided by 60 or 0.17. The second kind was 17 divided by 60 or 0.28. The third kind was 33 divided by 60 or 0.55.

The relative mass of the first kind would be 0.17 x 1.90g or 0.32g. The second kind would be 0.28 x 0.49g or 0.14g. The third kind would be 0.55 x 0.89 or 0.49g.

The atomic mass of candium then is 0.32g + 0.14g + 0.49g or 0.95g.

If I were to do another sample of candium, I think the atomic mass would be different. Even though the candy was well mixed, the different kinds were no always evenly found throughout the sample. The next sample might have 15 of the heaviest pieces or 25 of the lightest pieces.

Now, if I did two much larger samples, the numbers of the different kinds would be more similar so the relative abundances would be closer. That would make the atomic masses closer.

The relative abundances would have to add up to 1. There was 1 sample of sixty pieces. If I add up the numbers of each kind I get 60. The relative abundances have to add up to the whole as they are the fractions of the whole of each kind of candy. When I added them up, they did total 1.
About Atomic Mass:
As pointed out above, the numbers of protons and electrons in an atom do not change without changing important things about the atom. Neutrons are different. They do not determine the kind of atom. They do not affect the charge. What they do affect is the mass.

Protons have a mass of one atomic mass unit. This is a definition because the true masses of atoms are too small to work with: a number times ten to the negative twenty-third. That would be a decimal point followed by twenty-three zeros then a number.

Neutrons also have a mass of one atomic mass unit. So, if an atom has six protons and six neutrons, the protons make it carbon, the neutrons plus the protons give it a mass of twelve.

But not all carbon atoms have six neutrons. Some have seven. The more famous one has eight and is called carbon-14 [six protons plus eight neutrons give a mass of 14.]. Each different kind of carbon atom is called an isotope.

Just like in the candium lab, scientists find out how many neutrons atoms in a sample of an element have. In candium the normal number of neutrons would be found in the M&Ms. But almost as many would have one fewer neutron, think TicTacs in my sample or skittles in another kind of candium. Then there are a few with extra neutrons, the peanut candy pieces.

As we did for candium, scientists determine the atomic mass of each element. Since all known natural elements have more than one isotope, their atomic masses are not whole numbers.

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Looking at another box from the Periodic Table we see the name of the element. This one is carbon. Its symbol is C. Its atomic number is 6. As we noted in the last Project, the atomic number is the number of protons that an element has in its nucleus.

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The atomic number is the number of protons in the nucleus.

The mass number is the total amount of protons and neutrons in the nucleus.

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Science >> Chemistry for Kids

The atom is the basic building block for all matter in the universe. Atoms are extremely small and are made up of a few even smaller particles. The basic particles that make up an atom are electrons, protons, and neutrons. Atoms fit together with other atoms to make up matter. It takes a lot of atoms to make up anything. There are so many atoms in a single human body we won't even try to write the number here. Suffice it to say that the number is trillions and trillions (and then some more).

There are different kinds of atoms based on the number of electrons, protons, and neutrons each atom contains. Each different kind of atom makes up an element. There are 92 natural elements and up to 118 when you count in man-made elements.

Atoms last a long time, in most cases forever. They can change and undergo chemical reactions, sharing electrons with other atoms. But the nucleus is very hard to split, meaning most atoms are around for a long time.

Structure of the Atom

At the center of the atom is the nucleus. The nucleus is made up of the protons and neutrons. The electrons spin in orbits around the outside of the nucleus.

The Proton

The proton is a positively charged particle that is located at the center of the atom in the nucleus. The hydrogen atom is unique in that it only has a single proton and no neutron in its nucleus.

The Electron

The electron is a negatively charged particle that spins around the outside of the nucleus. Electrons spin so fast around the nucleus, scientists can never be 100% sure where they are located, but scientists can make estimates of where electrons should be. If there are the same number of electrons and protons in an atom, then the atom is said to have a neutral charge.

Electrons are attracted to the nucleus by the positive charge of the protons. Electrons are much smaller than neutrons and protons. About 1800 times smaller!

The Neutron

The neutron doesn't have any charge. The number of neutrons affects the mass and the radioactivity of the atom.

Other (even smaller!) particles

Quark - The quark is a really small particle that makes up neutrons and protons. Quarks are nearly impossible to detect and it's only recently that scientists figured out they existed. They were discovered in 1964 by Murray Gell-Mann. There are 6 types of quarks: up, down, top, bottom, charm, and strange.

Neutrino - Neutrinos are formed by nuclear reactions. They are like electrons without any charge and are usually travelling at the speed of light. Trillions and trillions of neutrinos are emitted by the sun every second. Neutrinos pass right through most solids including humans!

More Chemistry Subjects
Science >> Chemistry for Kids

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Science >> Chemistry for Kids The atom is the basic building block for all matter in the universe. Atoms are extremely small and are made up of a few even smaller particles. The basic particles that make up an atom are electrons, protons, and neutrons. Atoms fit together with other atoms to make up matter.

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Protons and Neutrons have about the same mass.

Protons have a positive charge, Neutrons have no charge, and Electrons have a negative charge .

Together they make a nucleus.

Electrons circle around the nucleus.