Question

answer the following questions.

1. lead has an atomic number of 82. how many protons and electrons does lead have?
2. oxygen has 8 electrons. how many protons does oxygen have?
3. zinc has 30 protons. what is its atomic number?
4. astatine has 85 protons. what is its atomic number?
5. rutherfordium has an atomic number of 104. how many protons and electrons does it have?
6. polonium has an atomic number of 84. how many protons and electrons does it have?
7. nobelium has an atomic number of 102. how many protons and electrons does it have?

in your textbook, read about isotopes and mass number.
determine the number of protons, electrons, and neutrons for each isotope described below.

1. an isotope has atomic number 19 and mass number 39.
2. an isotope has 14 electrons and a mass number of 28.
3. an isotope has 21 neutrons and a mass number of 40.

98 chemistry: matter and change • chapter 4

Explanation:

Step1: Recall atomic - number rule

The atomic number of an element is equal to the number of protons. In a neutral atom, the number of electrons is equal to the number of protons. The mass number is the sum of protons and neutrons.

Step2: Answer question 6

Lead has an atomic number of 82. So, the number of protons is 82. Since it is a neutral atom, the number of electrons is also 82.

Step3: Answer question 7

Oxygen has 8 electrons. Since in a neutral atom the number of electrons equals the number of protons, oxygen has 8 protons.

Step4: Answer question 8

Zinc has 30 protons. The atomic number is equal to the number of protons, so its atomic number is 30.

Step5: Answer question 9

Astatine has 85 protons. Its atomic number is 85 as atomic number = number of protons.

Step6: Answer question 10

Rutherfordium has an atomic number of 104. So, it has 104 protons. In a neutral atom, it has 104 electrons.

Step7: Answer question 11

Polonium has an atomic number of 84. It has 84 protons and 84 electrons (in a neutral atom).

Step8: Answer question 12

Nobelium has an atomic number of 102. It has 102 protons and 102 electrons (in a neutral atom).

Step9: Answer question 13

An isotope has an atomic number of 19. So, it has 19 protons. In a neutral atom, it has 19 electrons. The mass number is 39. Using the formula mass number = protons+neutrons, neutrons = mass number - protons = 39 - 19=20.

Step10: Answer question 14

An isotope has 14 electrons. So, it has 14 protons (in a neutral atom). The mass number is 28. Neutrons = mass number - protons = 28 - 14 = 14.

Step11: Answer question 15

An isotope has a mass number of 40 and 21 neutrons. Protons = mass number - neutrons = 40 - 21 = 19. In a neutral atom, electrons = protons = 19.

Answer:

1. 82 protons, 82 electrons
2. 8 protons
3. 30
4. 85
5. 104 protons, 104 electrons
6. 84 protons, 84 electrons
7. 102 protons, 102 electrons
8. 19 protons, 19 electrons, 20 neutrons
9. 14 protons, 14 electrons, 14 neutrons
10. 19 protons, 19 electrons, 21 neutrons