Answer:
Thus,there are 0.2 mole in 8 g of calcium.
Number 1 is Comets and asteroids
Number 2 is Comets are made of ice and rock
Number 3 is Meteor
Answer:
B. They don't understand how red shift affects stars.
Explanation:
Astronomers face difficulty in observing distant stars because they are so far that they are easily viewed by telescope. Light pollution is major concern in present times . There is very less window present for observation. The dim light from the distance stars also gets distorted due to atmosphere and effects astronomical seeing.
Astronomers are aware about the Doppler effect for light that is the redshift effect on the star light. It is not a difficulty for astronomers.
Answer:
Magnesium
Explanation:
Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray solid which bears a close physical resemblance to the other five elements in the second column of the periodic table: all group 2 elements have the same electron configuration in the outer electron shell and a similar crystal structure.
What you are looking for is something from the left side of the periodic table (the metals), combined with something from the right side of the periodic table.
SiCl4 is something from the middle with something on the right. Not the answer.
HCl is a possible answer, but it is not the best one, because Hydrogen can be on both sides. It is not quite as willing to give up its electrons as the answer.
CCl4 has the same problem as A.
The answer is C
Ca is in column 2 just about as far left as you can get.
Cl is in column 17 which is just about as far right as you can get.
