The mass of an atom of manganese is 54.9380u how many neutrons are contained in one atom of this elements

- There would be 30 neutrons.

Solution:-  We know that:

atomic mass = protons(mass of 1 proton) + neutrons(mass of 1 neutron)

atomic mass is given as 54.9380 u. Mass of proton is 1.0073 u and mass of neutron is 1.0087 u.

Atomic number for Mn is 25 means it has 25 protons. Let's plug in the values in the formula and calculate the number of neutrons for it.

54.9380 = 25(1.0073) + n(1.0087)

where n is the number of neutrons.

54.9380 = 25.1825 + 1.0087n

54.9380 - 25.1825 = 1.0087n

29.7555 = 1.0087n

n =

n = 29.5

It could be round to 30.

So, there would be 30 neutrons in an atom of Mn.

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.