The answer is either D or B. hope this helps.
To find the number of neutrons, you subtract the atomic number from the mass number of element X. So in this case, it'll be 151-44= the number of neutrons.
When Newlands tried to create a periodic table, his tried to conform to the "Rule of Octaves" he had discovered. He had the right idea, in that if you arrange the elements by atomic weight there would be similarities every 7 elements (not 8 because noble gases hadn't been discovered yet) but he tried to push this rule so much that he would put multiple elements in the same box to try to keep the rule. Mendeleev, however, left gaps in this table for undiscovered elements, which paved the way for our modern periodic table.
Answer:
1.402 * 10^2.
Explanation:
There are 3 digits before the decimal point so the exponent is 2.
