Answer: There are 
atoms of hydrogen are present in 40g of urea, 
.
Explanation:
Given: Mass of urea = 40 g
Number of moles is the mass of substance divided by its molar mass.
First, moles of urea (molar mass = 60 g/mol) are calculated as follows.
According to the mole concept, 1 mole of every substance contains 
atoms.
So, the number of atoms present in 0.67 moles are as follows.
In a molecule of urea there are 4 hydrogen atoms. Hence, number of hydrogen atoms present in 40 g of urea is as follows.
Thus, we can conclude that there are atoms of hydrogen are present in 40g of urea, .
The electrons always orbit around the nucleus, forming what is called an electron cloud. :)
The mass number of the daughter atom formed from the alpha decay of a certain radioactive atom that has 90 protons and 142 neutrons is 228.
<h3>What is alpha decay?</h3>
Alpha decay of a radioactive material is the release of an alpha particle that posseses mass number of 4 and atomic number of 2.
According to this question, a certain radioactive atom that has 90 protons and 142 neutron undergoes alpha decay. This means that the mass number of the daughter atom will be as follows:
Mass number of radioactive atom = 142 + 90 = 232
Mass number of daughter atom = 232 - 4 = 228
Therefore, the mass number of the daughter atom formed from the alpha decay of a certain radioactive atom that has 90 protons and 142 neutrons is 228.
Learn more about mass number at: brainly.com/question/4408975
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Hey there,
The answer is B, brittleness
Hope this helps :))
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