Question

name: ____________ period: date: ____________ isotope practice worksheet 1. what is an isotope? some protons in atomic nucleus 2. what does the number next to isotopes signify? 3. how can you tell isotopes apart? for each of the following isotopes, write the # of protons, neutrons, and electrons. chromium - 58 chromium - 63 # of protons 24 24 # of neutrons 34 39 # of electrons 24 24 carbon - 12 carbon - 16 # of protons 6 6 # of neutrons 6 10 # of electrons 6 6 nitrogen - 15 nitrogen - 20 # of protons 7 7 # of neutrons 8 13 # of electrons 7 7 sulfur - 23 sulfur - 25 # of protons 16 16 # of neutrons 7 9 # of electrons 16 16 sodium - 12 sodium - 20 # of protons 11 11 # of neutrons 1 9 # of electrons 11 11 selenium - 70 selenium - 75 # of protons 34 34 # of neutrons 36 39 # of electrons 34 34

Explanation:

Step1: Define isotopes

Isotopes are atoms of the same element with different numbers of neutrons in the atomic nucleus.

Step2: Meaning of number next to isotopes

The number next to an isotope (e.g., Carbon - 12) is the mass number, which is the sum of protons and neutrons in the nucleus.

Step3: Telling isotopes apart

Isotopes of the same element have the same number of protons but different numbers of neutrons.

Step4: Determine protons, neutrons and electrons

• Protons: The atomic number of an element gives the number of protons. For example, carbon has an atomic number of 6, so all carbon isotopes have 6 protons.
• Neutrons: Calculated as mass number - number of protons. For example, for Carbon - 12, neutrons = 12 - 6=6.
• Electrons: In a neutral atom, the number of electrons equals the number of protons.

Answer:

1. Isotopes are atoms of the same element with different numbers of neutrons in the atomic nucleus.
2. The number next to an isotope is the mass number, which is the sum of protons and neutrons in the nucleus.
3. Isotopes of the same element have the same number of protons but different numbers of neutrons.

For the isotopes in the tables:

• Chromium - 58: Protons = 24, Neutrons = 34, Electrons = 24
• Chromium - 63: Protons = 24, Neutrons = 39, Electrons = 24
• Carbon - 12: Protons = 6, Neutrons = 6, Electrons = 6
• Carbon - 16: Protons = 6, Neutrons = 10, Electrons = 6
• Nitrogen - 15: Protons = 7, Neutrons = 8, Electrons = 7
• Nitrogen - 20: Protons = 7, Neutrons = 13, Electrons = 7
• Sulfur - 23: Protons = 16, Neutrons = 7, Electrons = 16
• Sulfur - 25: Protons = 16, Neutrons = 9, Electrons = 16
• Sodium - 12: Protons = 11, Neutrons = 1, Electrons = 11
• Sodium - 20: Protons = 11, Neutrons = 9, Electrons = 11
• Selenium - 70: Protons = 34, Neutrons = 36, Electrons = 34
• Selenium - 75: Protons = 34, Neutrons = 39, Electrons = 34