The diagram shows molecules of Br2 and I2 drawn to the same scale. Which of the following is the best explanation for the difference in the boiling points of liquid Br2 and I2, which are 59°C and 184°C, respectively?  

Which of the following correctly compares periodic properties of two elements and provides an accurate explanation for that difference?

A student has samples of two pure compounds, XClO3 and ZClO3, which contain unknown alkali metals X and Z. The student measures the mass of each sample and then strongly heats the samples to drive off all the oxygen, leaving solid residues of XCl and ZCl. The student measures the mass of the solid residue from each sample. Which of the following questions can be answered from the results of the experiment?

Of the following electron configurations of neutral atoms, which represents an atom in an excited state?

Select the answer that best fits the statement: Is isomeric with CH3CH2CHO.

Which of the following best helps to explain why Na(s) is more reactive with water than Mg(s) is?

Which of the following correctly indicates whether the solid represented by the particulate model shown in the figure conducts electricity and explains why or why not?   The figure presents a particle diagram of a solid consisting of shaded circles, which represent negative ions, and smaller unshaded circles, which represent positive ions. The circles are organized in 5 rows and 5 columns, with negative ions and positive ions alternating. Ions that are adjacent are touching. The diagram shows a third dimension in the arrangement of ions. Another layer of negative ions is partly obscured by the positive ions.

What is the empirical formula of an oxide of chromium that is 48 percent oxygen by mass?

To determine the percentage of water in a hydrated salt, a student heated a 1.2346g sample of the salt for 30 minutes; when cooled to room temperature, the sample weighed 1.1857g. After the sample was heated for an additional 10 minutes and again cooled to room temperature, the sample weighed 1.1632g. Which of the following should the student do next?

Two identical spaceships are traveling in deep space, far from any planet or stars. The ships travel in the same direction, with the slower one directly behind the faster one. The ships are connected by a cable attached to a spool, so that part of the cable outside the ships can be made longer or shorter as needed. The cable is used to bring the ships to the same speed for a transfer of cargo. The graph above shows the speed of the two ships during a 10 second interval. Does at least one of the ships have its engine turned on during the time interval shown, and what evidence indicates so? The horizontal axis shows time from 0 to 10 seconds, and the vertical axis shows velocity from about 7990 to 8010 meters per second. Two sets of data points are plotted: solid dots for Ship 1 and open circles for Ship 2. Ship 1 starts near (0,8100) and trends to (10,8005). Ship 2 starts near (0,7990) and trends to (10,8005).