It's just a Phase
A sample has a mass of 36 g and a volume of 12 cm³. What is its density?
3.0 g/cm³
Convert 27°C to kelvin.
300 K
Which scientist’s atomic model included electrons within a region of positive charge—the “plum pudding” model?
J. J. Thomson
A neutral atom has 13 protons. Identify the element and give its number of electrons.
Aluminum; 13 electrons
Name the alkali metal in period 3.
Sodium; Na
An aluminum sample has a density of 2.70 g/cm³ and a volume of 10.0 cm³. What is its mass?
27.0 g
Convert 86°F to degrees Celsius.
30°C
Most particles passed straight through Rutherford’s gold foil. What did this suggest about the atom?
The atom is mostly empty space.
An oxygen-18 atom has 8 protons. How many neutrons does it have? How many electrons if it is neutral?
10 neutrons
8 electrons
Name a metalloid in group 14 and a noble gas in period 3.
Silicon or germanium; argon
A 24 gram piece of ice melts in a sealed container. What happens to the mass and volume occupied by the liquid water?
Mass remains 24 g because no matter leaves. The water occupies less volume because liquid water is denser than ice.
A sample boils at 80°C. Express this temperature in both Fahrenheit and kelvin.
176°F; 353 K.
A few particles in Rutherford’s experiment deflected sharply or bounced back. What did this suggest about the atom’s positive charge and mass?
Positive charge and most mass are concentrated in a small, dense nucleus.
A magnesium-25 ion has a charge of +2. Give its number of protons, neutrons, and electrons.
12 protons
13 neutrons
10 electrons
Mendeleev left gaps in his periodic table. Why was this a strength of his work?
He predicted undiscovered elements and their properties. Later discoveries supported his predictions.
A pure substance’s heating curve rises while it is liquid, then becomes horizontal as it boils. Which state or states are present during the horizontal section? Why does temperature stay constant?
Liquid and gas coexist during boiling. Added energy separates particles rather than increasing their average kinetic energy.
One sample is at 293 K and another is at 50°F. Which is warmer
293 K is warmer: 293 K = 20°C; 50°F = 10°C.
A student says, “If atomic models change, none of the earlier science was useful.” Explain why this is incorrect. Include a scientist or experiment.
Earlier models explain existing evidence and guide investigations. New evidence leads to revisions while supported findings remain. Rutherford revised Thomson’s model, but electrons remained part of the atom.
Particle X has 16 protons, 16 neutrons, and 18 electrons. Particle Y has 16 protons, 18 neutrons, and 16 electrons. Are they the same element? Are they isotopes? Give each charge.
Same element: sulfur. They are different isotopes because neutron counts differ. X: −2; Y: 0.
Draw a Bohr diagram for a neutral phosphorus-31 atom. Label the nucleus and show the electrons in each shell. (Note: I will only ask you to do one of the first 20 elements on the test)
Nucleus: 15 protons and 16 neutrons. Electrons: 2, 8, 5 across three shells. Award 100 each for protons, neutrons, total electrons, and shell arrangement.
A solid sample has a mass of 54.0 g and a volume of 20.0 cm³. It is at 35°C. One atom in the sample has 13 protons and 14 neutrons.
1. Calculate the sample’s density.
2. Convert its temperature to kelvin.
3. Identify the element and its mass number.
4. Give the number of electrons in each shell for the atom's neutral atom.
5. If the atom loses three electrons, what is its charge and how many electrons remain?
1. 2.70 g/cm³
2. 308 K
3. Aluminum-27
4. 1st: 2, 2nd: 8, 3rd: 3
5. +3 charge; 10 electrons