The radius of an atom of gold (au) is about 1.35 å. how many gold atoms would have to be lined up to span 5.0 mm ?

1.851.10⁷ gold atoms would have to be lined up to span 5.0 mm

There are 7 main quantities that have been determined based on international standards, namely:  

The length indicate the distance between two points in a place  

The symbol is usually expressed in l, length  

Length measurement can be used by several measuring instruments such as ruler, caliper length, meter, screw micrometer  

The main length unit consists of 7 units :

Each one unit descends then multiplied by 10, and if one unit increases then divided by 10  

For 1 Â (angstrom) equal to 10⁻⁷ mm

The radius of an atom of gold (Au) is about 1.35 Å

so the diameter = 1.35 x 2 = 2.7 Å = 2.7.10⁻⁷ mm

to be lined up to span 5.0 mm requires gold atoms :

amount of gold atom : 5.0 : 2.7.10⁻⁷ mm = 1.851.10⁷

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Keywords: gold atom, diameter, millimeters, angstrom(Å)

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hope this : -)

tony (lordcaos066)

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.