Answer:
C. fluorine (F) and chlorine (Cl)
D. arsenic (As) and antimony (Sb)
Explanation:
In the periodic table , all the elements are arranged according to the atomic number ,
and the elements are placed in groups and periods ,
The elements with similar chemical and physical properties are placed in a common group .
The elements present in the same group have the same number of valence electrons in the valence shell .
Hence , from the given options ,
fluorine (F) and chlorine (Cl) belongs to group 17 with 7 valence electrons in the outermost shell .
arsenic (As) and antimony (Sb) belong to group 15 with 3 valence electrons in the outermost shell .
I don’t understand the question
Answer:
B. 0.069 %
Explanation:
It should be initially noted in this answer in particular that, the amino acids tryptophan and tyrosine have a very precise 280 nm absorption rate, which allows a direct A280 size of protein concentration. The 280 nm UV absorbance rate is regularly utilized to approximate protein concentration in laboratories due to its simplistic nature, its affordability and also the ease of usage.
kindly check the attached image below for the solution to the above question.
Which type of telescope is most useful for detecting a star that emits very long electromagnetic waves?
A. a radio telescope B. an X-ray telescope C. an optical telescope D. a gamma ray telescope
A.)a radio telescope