02 Question (s points) See page 54 Cerium has four naturally occurring isotopes,

Question

02 Question (s points) See page 54 Cerium has four naturally occurring isotopes, listed in the table below. One isotope of cerium is far more abundant than any of the others. Determine the number of neutrons for each isotope and identify which isotope is the most abundant. Isotope mass (amu) 135.907 137.906 139.905 141.909 Isotope 3rd attempt Part 1 (1point) What is the number of neutrons in 136ce? 58 Part2 (1 point) 138c? What is the number of neutrons in Ce? 136 Part 3 (1 point) 140 What is the number of neutrons in Ce? Part 4 (1 point) 142c2 What is the number of neutrons in Ce? See Hint

Explanation / Answer

Ans. Note the following points-

I. Atomic number = number of protons = p

            II. Atomic mass = number of protons + number of neutrons = p + n

            III. The atomic number of an elements always remains constant. (Though atomic mass may differ depending on the isotopes).

            IV. Atomic number of Cerium = p = 58

# Part 1: Number of neutrons in 136Ce = Atomic mass – atomic number

                                                            = 136 – 58

                                                            = 78

# Part 2: Number of neutrons in 138Ce = 138 – 58 = 80

# Part 3: Number of neutrons in 140Ce = 140 – 58 = 82

# Part 4: Number of neutrons in 142Ce = 142 – 58 = 84

# 140Ce is the most abundant isotope of the element.

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