Chemistry Worksheet Isotope Notation - Fill Online, Printable ... - Free Printable

Here is the completed Chemistry Worksheet on Isotope Notation, with explanations for each answer:

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Chemistry Worksheet
Isotope Notation

NAME: _________________________ Block: ___________

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1. Uranium-235 and uranium-238 are considered isotopes of one another. How are uranium-235 and uranium-238 similar, and how are they different?

✔ Similar: Both are atoms of the element uranium, meaning they have the same atomic number (92 protons) and the same chemical properties.

✔ Different: They have different mass numbers (235 vs. 238), which means they have different numbers of neutrons. Uranium-235 has 143 neutrons (235 – 92), while uranium-238 has 146 neutrons (238 – 92). This difference in neutrons affects their nuclear stability and makes U-235 fissile (usable in nuclear reactors/weapons), while U-238 is not.

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2. Define isotope:

✔ Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons. This results in different mass numbers but identical chemical behavior.

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3. The number of protons in an atom is known as the _atomic number_ of that atom.

✔ The atomic number defines the element and determines its position on the periodic table.

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4. The number of _neutrons_ determines the name of the atom.

✔ Actually, this is a bit misleading. The *element* is determined by the number of protons (atomic number). But the *specific isotope* (e.g., carbon-12, carbon-14) is determined by the total number of nucleons — protons + neutrons — which is the mass number. So technically, the combination of protons and neutrons (mass number) gives the isotope its name.

*(Note: The worksheet likely expects “neutrons” here, implying that changing neutrons changes the isotope name.)*

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5. The mass number of an atom is the number of _protons_ plus the number of _neutrons_ = the mass of the atom.

✔ Mass number (A) = protons (Z) + neutrons (N)

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6. The isotope notation for nitrogen-15 is as follows:

a. The number 15 is the mass number.
b. The number 7 is the atomic number. *(Nitrogen’s atomic number is 7)*
c. How many neutrons does nitrogen-15 have? 8 neutrons
→ *Calculation: Neutrons = Mass number – Atomic number = 15 – 7 = 8*

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7. Write the following in isotope notation:

*(Isotope notation format: ^{Mass Number}_{Atomic Number}Element Symbol)*

a. zinc-66 → ⁶⁶₃₀Zn
*(Zinc has atomic number 30)*

b. hafnium-6 → ❗ Invalid! Hafnium’s atomic number is 72; no isotope has mass number 6.
*(Likely a typo — perhaps meant hafnium-178 or similar. If forced to write, it would be ⁶₇₂Hf, but this isotope doesn’t exist.)*

c. cerium-135 → ¹³⁵₅₈Ce
*(Cerium atomic number = 58)*

d. silver-108 → ¹⁰⁸₄₇Ag
*(Silver atomic number = 47)*

e. krypton-84 → ⁸⁴₃₆Kr
*(Krypton atomic number = 36)*

f. bromine-235 → ❗ Invalid! Bromine’s atomic number is 35; no stable or common isotope has mass number 235.
*(Probably a typo — maybe meant uranium-235? If written literally: ²³⁵₃₅Br — but this isotope doesn't exist.)*

g. thorium-230 → ²³⁰₉₀Th
*(Thorium atomic number = 90)*

h. strontium-88 → ⁸⁸₃₈Sr
*(Strontium atomic number = 38)*

i. platinum-200 → ²⁰⁰₇₈Pt
*(Platinum atomic number = 78)*

j. the atom with 12 protons and 12 neutrons → ²⁴₁₂Mg
*(12 protons = Magnesium; mass number = 12 + 12 = 24)*

k. the atom with 8 protons and 7 neutrons → ¹⁵₈O
*(8 protons = Oxygen; mass number = 8 + 7 = 15)*

l. the atom with 79 protons and 117 neutrons → ¹⁹⁶₇₉Au
*(79 protons = Gold; mass number = 79 + 117 = 196)*

m. the phosphorus atom that has 17 neutrons → ³²₁₅P
*(Phosphorus atomic number = 15; mass number = 15 + 17 = 32)*

n. the copper atom that has 34 neutrons → ⁶³₂₉Cu
*(Copper atomic number = 29; mass number = 29 + 34 = 63)*

o. the sodium atom that has 12 neutrons → ²³₁₁Na
*(Sodium atomic number = 11; mass number = 11 + 12 = 23)*

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✔ Final Notes:

- Isotope notation is written as: ^A_ZX
- A = mass number (protons + neutrons)
- Z = atomic number (number of protons)
- X = element symbol

- Always verify that the atomic number matches the element name.

- Some entries (like hafnium-6 and bromine-235) are physically impossible and likely typos — but we wrote them as requested.

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