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An atom of lead (Pb) has a mass number of 207. How many neutrons are in the nucleus?

A. 130

B. 125

C. 82

D. 84

Answer Explanation:

We find the number of neutrons as follows

Number of neutrons

= mass number – atomic number

= 207 – 82

= 125 neutrons

Therefore, the Correct Answer is B.

Q #1: Which of these infectious agents do not have nucleic acid?

A. viroids

B. viruses

C. bacteria

D. prions

Answer Explanation
Q #2: Which of these processes occurs in the mouth?

A. Ingestion

B. Mechanical digestion

C. Chemical digestion

D. All of the above

Answer Explanation

All of these processes occur in the mouth. Ingestion involves taking food into the mouth, mechanical digestion includes the physical breakdown of food through chewing and mixing with saliva, and chemical digestion begins with the action of enzymes in saliva, such as amylase, which starts to break down carbohydrates.
Q #3: An atom of lead (Pb) has a mass number of 207. How many neutrons are in the nucleus?

A. 130

B. 125

C. 82

D. 84

Answer Explanation

We find the number of neutrons as follows

Number of neutrons

            = mass number – atomic number

            = 207 – 82

            = 125 neutrons

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