Question

2. Perform this operation and report the answer to the correct number of significant figures: What is the mass of a cube of aluminum that is 4.0 cm on each edge? The density of aluminum is 2.7 g/cm3. Show all calculations leading to an answer.
3. Explain why a model of the atom is crucial to understanding chemistry and in explaining the behavior of matter. Use 3 - 4 sentences in your explanation.

4. What parts of Dalton’s atomic theory no longer agree with the current picture of the current picture of the atom? Provide an answer using at least 3 to 4 complete content related sentences in your own words.

5. If an element has 12 protons and 17 neutrons, how many electrons must it have?

Answer 1

2) D = m/V. Knowns: V = (4 x 4 x 4) = (64) D = 2.7

2.7 = m/(64)

172.8 = m or with significant figures, 170

3) Knowing the model of the atom is crucial becuase without understanding what everything is made up of, then there is no way of telling how it is going to react with outside things. Knowing the model of the atom can better help us visualize what it looks like and it can also tell us how it is going to react baced on its propertys and what it is made of.

4) Dalton's theory tells us that 1, all matter is made of atoms, which are indivisible and indestructiable. This does not agree with todays findings because we know that atoms can be broken up into sub atomic particals, and even those sub atomic particals can be broken down even further to sub-sub-atomic particals such as quarks and borons. 2, We also know about Isotopes. Isotopes are the same atom but with different atomic weights becaus of the amount of nutrons in the nuclei.

5) If an element has 12 protons and 17 neutron, in order to be stable and found in nature, the atom must have 12 protons because protons are positive and neutrons have a charge of 0 so in order to balence the atom out, the electrons, with a negitive charge, must be the same number as the protons.