Which of the models shown below best represents the modern understanding of the structure of the atom? Two small green balls and two small red balls labeled with plus signs are clustered at the center of a larger circle. Two small yellow circles labeled with minus signs lie on the outer circle, directly across from each other.
Model A

A red ball is shown, with a plus sign faintly visible on it. The ball contains 10 smaller orange balls, each labeled with a minus sign.
Model B

Atomic Structure
Model C

Photos by Phrood and Furmanj

Model A

Model B

Model C

Why is the bond angle in a water molecule less than the bond angle of methane? a. the central oxygen atom in water has two lone pairs of electrons, whereas the central carbon atom in methane has no lone pairs. b. the central hydrogen atom in water has one lone pair of electrons, whereas the central carbon atom in methane has two lone pairs. c. the central oxygen atom in water has four lone pairs of electrons, whereas the central carbon atom in methane has only one lone pair. d. the central oxygen atom exerts more repulsive force on surrounding atoms than the central carbon atom in methane does. reset next

Which of the following is the correct formula for copper (i) sulfate trihydrate? cuso4 · 3h2o cuso4(h2o)3 cu2so4(h2o)3 cu2so4 · 3h2o

Select the most likely product for this reaction: koh(aq) + co2(g) – ? k2co3(aq) + h2o(1) k(s) + h2(g) + o2(g) k(s) + co3(9) +h2