Question

part iv - reflection questions

1. which particles contribute to the mass number and which do not? why?
2. which particle contributes to the atomic number and why?
3. which particles contribute to the net charge and how does each change the net charge?

part v - isotopes
for all elements the number of neutrons can make the nucleus stable or unstable. the nuclear strong interaction (also called the nuclear strong force or nuclear force) is what holds the nucleus together. neutrons help hold the protons the right distance apart from each other to maintain nuclear stability.
different isotopes of the same element are written in words and symbols to show the mass number (recall that mass number is the number of protons and neutrons). for example, the two isotopes of carbon that were discussed were carbon - 12 and carbon - 14. the symbolic notation for these two isotopes would be:
₆¹²c for carbon 12 with an atomic number of 6 and a mass number of 12.
₆¹⁴c for carbon 14 with an atomic number of 6 and a mass number of 14
activity:

1. start by creating the isotope oxygen - 16. this will have 8 protons, 8 neutrons, and 8 electrons.

a. what is the symbolic notation for this isotope?
b. is this isotope stable or unstable?

1. add a neutron to the atom

a. what element is this now?
b. what is the name of this isotope?
c. what is the symbolic notation for this isotope?

1. add another neutron to the atom. you should have 8 protons, 10 neutrons, and 8 electrons.

a. what element is this now?
b. what is the name of this isotope?
c. what is the symbolic notation for this isotope?
d. is this isotope stable or unstable?

1. based on this activity, when we say something is “radioactive” what do you think we mean? use the word neutron in your answer.

Explanation:

Step1: Identify particles contributing to mass number

Protons and neutrons have significant mass and contribute to mass number. Electrons have negligible mass and do not contribute.

Step2: Identify particle contributing to atomic number

The atomic number is the number of protons in an atom. So protons contribute to the atomic number.

Step3: Identify particles contributing to net charge

Protons have a +1 charge, electrons have a - 1 charge. Protons increase positive net - charge, electrons increase negative net - charge. Neutrons have no charge and do not contribute to net charge.

Step4: Symbolic notation for oxygen - 16

The atomic number of oxygen is 8. For oxygen - 16 with 8 protons and 8 neutrons, the symbolic notation is $^{16}_{8}O$. It is a stable isotope.

Step5: After adding one neutron

The element is still oxygen as the number of protons remains 8. The isotope is called oxygen - 17, and the symbolic notation is $^{17}_{8}O$.

Step6: After adding another neutron

The element is oxygen. The isotope is called oxygen - 18, and the symbolic notation is $^{18}_{8}O$. Oxygen - 18 is a stable isotope.

Step7: Definition of radioactive

When an isotope has an unstable nucleus due to an imbalance in the number of neutrons and protons, it is radioactive. Unstable isotopes will decay over time to become more stable, emitting radiation in the process.

Answer:

1. Protons and neutrons contribute to the mass number because they have significant mass. Electrons do not contribute as their mass is negligible.
2. Protons contribute to the atomic number as the atomic number is the number of protons in an atom.
3. Protons contribute a +1 charge (increase positive net - charge), electrons contribute a - 1 charge (increase negative net - charge), neutrons do not contribute as they have no charge.
4. a. $^{16}_{8}O$

b. Stable

1. a. Oxygen

b. Oxygen - 17
c. $^{17}_{8}O$

1. a. Oxygen

b. Oxygen - 18
c. $^{18}_{8}O$
d. Stable

1. When an isotope has an unstable nucleus due to an inappropriate number of neutrons (causing an imbalance with protons), it is radioactive and will decay over time, emitting radiation.