Which statement is true about electronegativity? a. the size of an atom and the number of valence electrons determine an atom's electronegativity. b. electronegativity increases as the number of protons in an atom decreases. c. electronegativity is the ability of an atom to attract electrons. d. a very electronegative atom gives up electrons quickly in reactions

Electronegativity is a measure of the ability of an atom to attract electrons. The value tends to increase on moving from left to right across a period in the periodic table. This is because as the atomic number increases so does the nuclear charge which causes the added electron to experience a stronger nuclear attraction.

For example, if the consider the second period, then Lithium which is present in the extreme left will show a greater tendency to lose electrons (lower electronegativity) while Fluorine present in the extreme right will show a greater tendency to attract electrons and therefore high electronegativity. Thus, when Li and F combine, they form what is called an ionic bond.

Ans C) True statement

Electronegativity generally increases from left to right across a period.

1. the question asks the most appropriate, which seems to rule out "all of the above." your choice appears to be the correct one.

2. the protocol described is good for identifying correlation, but not cause and effect. for cause/effect, you need to devise a protocol that will assign the treatment (or not) to groups that have essentially the same "demographics" with respect to all the other variables. your choice regarding control group seems appropriate. random assignment of treatment (choice d) may be appropriate also. (i think you can argue that b and d are just different descriptions of the same method.)

3. d will randomize the birds, but may not guarantee there are 10 in each group. e will do both, so seems the better choice.

comment on question 2

based on the problem statement, it seems clear that confident, attentive drivers are more likely to use daytime running lights. so, the protocol might need to be devised in such a way that the lights would be turned on or off without the driver's knowledge. (an attentive driver will figure it out.) assigning a confident, attentive driver to a group required to drive without running lights might mess with his/her confidence and attentiveness. you don't want your experiment to do that. (nor do you want the experiment to subject a driver to greater risk of accident as a consequence of driving without running lights.) experiments involving human safety are always problematic.