Philosophical Idea to Scientific Theory
According to the law of conservation of mass, if element A has an atomic mass of 2 amu and element B has an atomic mass of 3 amu, what would be the expected mass for compound AB? A2B3?
AB 5 mass units
A2B3 would be 13 mass units
The smallest particles of an element that still retains the properties of the element.
What is the atom
Atoms of an element that have the same number of protons but different number of neutrons (different mass number).
Hydrogen-3 and Hydrogen-2
If 63.5 g of Cu combine with 16 g of O to form CuO, how many grams of O will be needed to combine with the same amount of Cu to form CuO2?
32 g of O
Which subatomic particle has a charge of +1
proton
Explain how Dalton's atomic theory provided evidence for the law of conservation of mass.
Because all chemical reactions are only the rearrangement of atoms, mass is neither created or destroyed during such changes.
Rutherford discovered two things about the atom from his experiment. What was the name of his experiment and what are the two main things he discovered about the atom?
The atom has a positively charged nucleus.
The atom is mostly empty space
The gold foil experiment
Give me the number of protons, neutrons, and electrons in the following isotopes.
Protium, Deuterium, and Tritium
Protium has 0 N, Deuterium has 1 N, and Tritium has 2 N
If 4.0 g of element A combine with 10.0 g of element B, then 12 g of element A combine with ____ g of element B.
30 g of element B
4/10 = 12/x
What makes up the mass of an atom?
Protons and neutrons
No matter how few sodium chloride crystals one inspects, the mass percentage of sodium to chloride remains unchanged. What law does this describe?
The law of definite proportions.
What did Thompson discover about the atom that Dalton was incorrect about? Name the experiment that Thompson used.
The atom was actually divisible and he discovered the negatively charged electron using the Cathode Ray Experiment.
Suppose you have a sample of an element. How is the mass in grams of the element converted to amount in moles.
Divide by molar mass (g/mol)
Determine the mass in grams of 3.01 x 1023 atoms of Cl
17.7 g
3.01 x 1023 atoms x 1 mol/6.022 x 1023 x 35.45 g/1 mol
If you have 1 mole of Argon-40 and 1 mole of Potassium-40, which one has more atoms per mole?
They both have 6.022 x 1023 atoms in a mole.
State the law of multiple proportions and give an example of two compounds that illustrate the law.
If two or more compounds are composed of the same two elements, then the ratio of the masses of the second element combined with a certain mass of the first element, is always a ratio of small whole numbers. ex. CO and CO2
What is a nuclide?
Any isotope of any element
Suppose you have a sample of an element. How is the mass in grams of the element converted to number of atoms?
Divide by molar mass, then multiply by Avogadro's number.
Beaker A contains 2.06 mol of Copper and Beaker B contains 222 grams of Silver. Which beaker contains the larger mass? Which beaker has the larger number of atoms?
Beaker B has the larger mass.
Both beakers contain the same number of atoms.
Mass of silver 2.06mol x 63.55 g/1mol = 130.9 g
222g Ag x 1 mol/107.87 g = 2.06 mol
Which atom has more neutrons, potassium-40 or argon-40?
Argon-40 has 22 neutrons (40-18)
Potassium-40 has 21 neutrons (40-19)
List the five main points of Dalton's Atomic Theory
1. All matter is composed of atoms. 2. All atoms of the same element are identical and atoms of diff elements are different. 3. Atoms cannot be subdivided, created or destroyed. 4. Atoms of different elements combine in whole number ratios to form compounds. 5. In chemical compounds atoms are separated, combined and rearranged.
Cathode rays emitted by a piece of silver and a piece of copper illustrates identical properties. What is the significance of this observation?
All cathode rays are the same regardless of the source. Therefore, the particles responsible for the cathode rays must be present in all atoms.
Write the nuclear symbol and hyphen notation for the following isotopes:
a. Mass number of 28
b. 26 electrons and 30 neutrons
Silicon-28
Iron-56
Calculate the number of atoms in 10.0 g of sulfur.
1.88 x 1023 atoms S
10.0 g x 1 mol/32.07g x 6.022 x 1023/1 mol
How many proton, neutrons, and electrons are in Mg2+
12 Protons
12 Neutrons
10 Electrons