Free Printable Atomic Structure And Isotopes Worksheets - Free Printable

Let's solve each question on the Atomic Structure & Isotope Worksheet step by step and provide clear explanations.

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1. The mass of an atom is contained mainly in its ________ and ________.

✔ Answer: protons and neutrons

🔹 Explanation: Protons and neutrons are located in the nucleus and have nearly identical masses (about 1 atomic mass unit each). Electrons have very little mass (~1/1836 of a proton), so they contribute negligibly to the total mass.

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2. The identity of an element is determined by its number of ________.

✔ Answer: protons

🔹 Explanation: The number of protons (atomic number) defines the element. For example, all atoms with 6 protons are carbon atoms, regardless of neutron or electron count.

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3. Isotopes are atoms with the same number of ________ and different number of neutrons.

✔ Answer: protons

🔹 Explanation: Isotopes are variants of the same element that have the same number of protons but different numbers of neutrons. For example, carbon-12 and carbon-14 both have 6 protons but different neutrons.

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4. The charge of an atom or ion is determined by its number of ________.

✔ Answer: electrons

🔹 Explanation: Atoms are neutral when the number of protons equals electrons. Ions form when electrons are gained or lost. So, the charge depends on the difference between protons and electrons:
Charge = protons – electrons

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5. What is the central core of an atom called?

✔ Answer: c) nucleus

🔹 Explanation: The nucleus is the dense center of the atom containing protons and neutrons.

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6. An atom with a charge is known as an

✔ Answer: d) ion

🔹 Explanation: When an atom gains or loses electrons, it becomes charged — this is called an ion.

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7. An atom with equal number of protons and electrons is called

✔ Answer: b) neutral atom

🔹 Explanation: Equal protons and electrons mean no net charge → neutral atom.

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8. Isotopes have

✔ Answer: b) different number of neutrons

🔹 Explanation: By definition, isotopes have the same number of protons but different numbers of neutrons.

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9. An isotope of carbon is

✔ Answer: c) carbon-14

🔹 Explanation: Carbon has atomic number 6. Carbon-14 means it has 6 protons and 8 neutrons (14 - 6 = 8). It’s a well-known isotope of carbon.
Other options:
- Boron-12 → not carbon
- Nitrogen-12 → nitrogen (7 protons)
- Hydrogen-2 → deuterium, not carbon

So only carbon-14 is an isotope of carbon.

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10. Fill in the table

We’ll use these formulas:
- Atomic number (Z) = number of protons
- Mass number (A) = protons + neutrons
- Charge = protons – electrons
- If charge ≠ 0 → it’s an ion
- Nuclear symbol: $ ^{A}_{Z}\text{X} $

Let’s go row by row:

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#### Row 1:
- Protons: 47 → Atomic number = 47 → Element: Silver (Ag)
- Neutrons: 63 → Mass number = 47 + 63 = 110
- Electrons: 47 → same as protons → neutral
- Is it an ion? No → charge = 0
- Nuclear symbol: $ ^{110}_{47}\text{Ag} $

✔ Answer:
- Element name: Silver
- Ion? No
- Charge: 0
- Nuclear symbol: $ ^{110}_{47}\text{Ag} $

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#### Row 2:
- Protons: 15 → Atomic number = 15 → Element: Phosphorus (P)
- Neutrons: 17 → Mass number = 15 + 17 = 32
- Electrons: 15 → same as protons → neutral
- Not an ion → charge = 0
- Nuclear symbol: $ ^{32}_{15}\text{P} $

✔ Answer:
- Element name: Phosphorus
- Ion? No
- Charge: 0
- Nuclear symbol: $ ^{32}_{15}\text{P} $

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#### Row 3:
- Protons: 12 → Atomic number = 12 → Element: Magnesium (Mg)
- Neutrons: 12 → Mass number = 12 + 12 = 24
- Electrons: 12 → same as protons → neutral
- Not an ion → charge = 0
- Nuclear symbol: $ ^{24}_{12}\text{Mg} $

✔ Answer:
- Element name: Magnesium
- Ion? No
- Charge: 0
- Nuclear symbol: $ ^{24}_{12}\text{Mg} $

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#### Row 4:
- Protons: 12 → Magnesium again
- Neutrons: 13 → Mass number = 12 + 13 = 25
- Electrons: 12 → same as protons → neutral
- Not an ion → charge = 0
- Nuclear symbol: $ ^{25}_{12}\text{Mg} $

✔ Answer:
- Element name: Magnesium
- Ion? No
- Charge: 0
- Nuclear symbol: $ ^{25}_{12}\text{Mg} $

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#### Row 5:
- Protons: 28 → Atomic number = 28 → Element: Nickel (Ni)
- Neutrons: 32 → Mass number = 28 + 32 = 60
- Electrons: 27 → fewer than protons → positive ion
- Charge = 28 – 27 = +1
- So it's a cation: Ni⁺
- Nuclear symbol: $ ^{60}_{28}\text{Ni}^{+} $ or just $ ^{60}_{28}\text{Ni} $ with charge noted

✔ Answer:
- Element name: Nickel
- Ion? Yes → charge = +1
- Nuclear symbol: $ ^{60}_{28}\text{Ni}^{+} $

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✔ Final Table Filled In:

| Protons | Neutrons | Electrons | Element Name | Is it an ION? If so, what is the charge? | Nuclear Symbol |
|--------|---------|----------|--------------|-------------------------------------------|----------------|
| 47 | 63 | 47 | Silver | No | $ ^{110}_{47}\text{Ag} $ |
| 15 | 17 | 15 | Phosphorus | No | $ ^{32}_{15}\text{P} $ |
| 12 | 12 | 12 | Magnesium | No | $ ^{24}_{12}\text{Mg} $ |
| 12 | 13 | 12 | Magnesium | No | $ ^{25}_{12}\text{Mg} $ |
| 28 | 32 | 27 | Nickel | Yes, +1 | $ ^{60}_{28}\text{Ni}^{+} $ |

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✔ Summary of Answers:

1. protons and neutrons
2. protons
3. protons
4. electrons
5. c) nucleus
6. d) ion
7. b) neutral atom
8. b) different number of neutrons
9. c) carbon-14
10. See completed table above.

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