Question 33 of 42beginner🔧 ApplyNumerical2 marks

An atom 70X has 31 electrons. How many neutrons are there in its nucleus?

Correct Answer

39

Exercise: EXERCISES | Q: 11 | (Page 21)
For More Understanding

Explanation

The superscript in the notation 70^{70}X represents the Mass number, which is 70. For a neutral atom, the number of protons is equal to the number of electrons. Since the atom has 31 electrons, it contains 31 protons. Using the relationship from the text, Mass number = Number of protons + Number of neutrons, we can rearrange it to find the neutrons: Number of neutrons = Mass number - Number of protons. Substituting the known values, Number of neutrons = 70 - 31 = 39.

Solution Steps

  1. Step 1: Identify the Mass number from the notation 70^{70}X, which is 70.

  2. Step 2: Determine the Number of protons. Since the atom has 31 electrons, it must have 31 protons.

  3. Step 3: Calculate the Number of neutrons using the formula: Number of neutrons = Mass number - Number of protons = 70 - 31 = 39.

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