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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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