Ben and sam were conducting experiments on physical and chemical changes in science class. first they added some salt to water and stirred it up until the salt dissolved. "that's a physical change" ben said. "and that's a solution which is a mixture", added sam. next they added an anti-acid tablet to some water. the water began to fizz and bubble. the beaker got cooler. "that's a physical change too," ben noted. "no, it's not," responded sam. who is correct and where should the contents of the beaker be placed in the venn diagram?

The atomic radius of sodium is 186 pm and of chlorine is 100 pm. the ionic radius for na+ is 102 pm and for cl– is 181 pm. in going from na to cl in period 3, why does the atomic radius decrease while the ionic radius increases? a. the inner electrons in the sodium cation shield its valence electrons more effectively than the inner electrons in the chloride anion do. b. the inner electrons shield the valence electrons more effectively in the chlorine atom than in the chloride anion. c. the outermost electrons in chloride experience a smaller effective nuclear charge than those in the sodium cation do. d. the outermost electrons in chloride experience a larger effective nuclear charge than those in the sodium cation do. e. monatomic ions are bigger than the atoms from which they are formed.

Voltaic cells produce a positive overall charge. what does this indicate? a. the reaction is likely to be endothermic. b. the reaction is spontaneous. c. the reaction is not likely to occur. d. the reaction is not spontaneous.

Who discovered a pattern to the elements in 1869?