S orbital.
Group 1 elements have a general configuration 
, where n represents the highest occupied Principal Energy Level. For example, Lithium has the valence configuration 
whereas Cesium has 
. Both of them belong to Group 1 of Periodic Table.
Group 2 elements have a general configuration of 
. For example, Magnesium has 
as its outer shell configuration while Strontium has the same as 
.
We see that in both the cases, the outermost S orbital is being filled.
Answer:
her displacement <em>s=337.5m</em>
Explanation:
check out the above attachment ☝️
Answer:
agree with student 2, disagree with student 1
Explanation:
If you want to know if the wavelength of light was shifted you have to know the original wavelengths
Since we know the absorption spectrum for elements like hydrogen, we can look for these absorption lines in the star's spectra and figure out what direction these lines are shifted and tell if the star is moving away or towards us
The color of the star refers to the temperature of the star's surface which is not related to the doppler shift of the star
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