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2.5 The Structure of the Atom -- Part 3
Since the early 1990s, researchers have successfully applied mass spectrome try to biological molecules, including the workhorse molecule in cells and the molecule that carries genetic information.
Modern techniques have overcome the problem of not being able to analyze these molecules by mass spectrometry because they were difficult to ionize without being destroyed.
Mass spectrometry can now be used to determine whether a tumor contains any cancer-causing genes.
There are between 41 and 50 shrimp per pound.
Each tiger prawn can weigh up to a pound, which is why they have low counts.
The advantage of categorizing shrimp this way is that we can count them.
Two pounds of shrimp contains between 81 and 100 shrimp.
There is a similar concept for atoms.
As a chemist, we often need to know the number of atoms in a sample of a given mass, which is more difficult than counting atoms.
The elements have particles that are atoms.
When hydrogen and oxygen combine to form water, there are two hydrogen atoms and one oxygen atom.
If we want to know how much hydrogen to react with a given mass of oxygen to form water, we need to know the number of atoms.
We need to know the mass of hydrogen that is twice the number of atoms.
IV fluids can be delivered to patients by directly dripping them into veins.
The fluids must have a specific number of sodium and chloride ion per liter.
The properties of the fluid are influenced by the number of particles.
Administering the wrong number of fluids could be fatal.
Atoms are too small to be counted.
Even if you could count the atoms in a single day, you wouldn't be able to count the number of atoms in a sand grain.
We count the number of atoms by weighing them.
We use units such as a dozen (12 objects) or a gross (14 objects) to organize our counting and keep our numbers manageable.
We need a larger number of atoms for this purpose.
There are 22 copper pennies.
The mole can tell Avogadro's number of anything.
One mole of marbles and one mole of sand grains correspond to 6.022 and 1023, respectively.
The objects of everyday sizes are made up of one mole of atoms.
Twenty-two copper pennies have about 1mol of copper atoms, and 1 ounce of water has about 1 mol of water molecule.
The mole's specific value is the second fundamental thing to understand.
The mole gives us a relationship between mass and copper.
We can count atoms by weighing them.
It's similar to converting between dozens of eggs and number of eggs.
You can use the conversion factor for eggs.
The conversion factor for atoms is 6.022 * 1023 atoms.
One mol of water is equivalent to 6.022 ounces.
This example shows how to use conversion factors.
The number of copper atoms is calculated.
The person asked to find the number of copper atoms.
To get to the number of Cu atoms, you need a mol Cu Avogadro's number.
The answer is large since atoms are small.
The number of moles of copper is close to 2.5, so the number of atoms is close to Avogadro's number.
A ring has 2.80 silver atoms.
The mass of 1 mol of atoms is needed to count atoms by weighing them.
The mass of 1 mol of atoms is equal to the atomic mass of carbon-12 in atomic mass units.
The same relationship holds for all elements since the mass of all other elements is compared to carbon-12.
The element's atomic mass in atomic mass units is equal to the element's molar mass in grams per mole.
The atomic mass of copper is 63.55 amu and the molar mass is 63.55 g/mol.
One mole of copper atoms has a mass of 63.55 g.
The two dishes have the same number of objects, but the mass is different because peas are smaller.
A mole of light atoms has less mass than a mole of heavier atoms.
The conversion factor between the mass and the amount of that element is called the molar mass.
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