Atomic Structure and Isotopes Worksheet With Answers | PDF - Free Printable

Here are the step-by-step solutions to the Atomic Structure & Isotope Worksheet.

Part 1: Fill in the Blanks

1. Question: The mass of an atom is contained mainly in its \_\_\_\_\_\_ and \_\_\_\_\_\_.
* Reasoning: An atom consists of protons, neutrons, and electrons. Electrons have almost no mass. Protons and neutrons are heavy particles located in the center.
* Answer: protons; neutrons (or nucleus)

2. Question: The identity of an element is determined by its number of \_\_\_\_\_\_.
* Reasoning: If you change the number of neutrons, it becomes an isotope. If you change electrons, it becomes an ion. But if you change the proton count, the element itself changes (e.g., Carbon has 6, Nitrogen has 7).
* Answer: protons

3. Question: Isotopes are atoms with the same number of \_\_\_\_\_\_ and different number of neutrons.
* Reasoning: By definition, isotopes are versions of the same element. To be the same element, they must have the same atomic number (protons), but they can vary in weight (neutrons).
* Answer: protons

4. Question: The charge of an atom or ion is determined by its number of \_\_\_\_\_\_.
* Reasoning: Charge comes from the balance between positive protons and negative electrons. If these numbers don't match, there is a charge.
* Answer: protons and electrons

---

Part 2: Multiple Choice

5. Question: What is the central core of an atom called?
* Reasoning: The center containing the protons and neutrons is called the nucleus.
* Answer: c) nucleus

6. Question: An atom with a charge is known as an...
* Reasoning: A neutral atom has equal protons and electrons. When the balance is off, creating a positive or negative charge, it is called an ion.
* Answer: d) ion

7. Question: An atom with equal number of protons and electrons is called...
* Reasoning: Positive charges cancel out negative charges when the amounts are equal, resulting in zero net charge. This is a "neutral" atom.
* Answer: b) neutral atom

8. Question: Isotopes have...
* Reasoning: Referencing question #3, isotopes differ specifically because they have different masses due to varying neutron counts.
* Answer: b) different number of neutrons

9. Question: An isotope of carbon is...
* Reasoning: An isotope must be the same element name. Boron and Nitrogen are different elements. Hydrogen-2 is hydrogen. Carbon-14 is carbon (with extra neutrons).
* Answer: c) carbon-14

---

Part 3: The Table

*Logic for filling the table:*
* Element Name: Determined by the number of Protons (Atomic Number).
* Is it an ION? Check if Protons $\neq$ Electrons.
* If Protons > Electrons = Positive (+) Ion.
* If Protons < Electrons = Negative (-) Ion.
* If Protons = Electrons = Neutral (No charge).
* Nuclear Symbol: Format is usually ${}^{A}_{Z}\text{X}$ where X is symbol, Z is protons, A is mass (Protons + Neutrons). Or simply Element-Mass.

Row 1:
* Data: P=47, N=63, E=47
* Name: Atomic number 47 is Silver (Ag).
* Ion Check: 47 protons vs 47 electrons. They are equal. It is Neutral.
* Symbol: Mass = $47 + 63 = 110$. Symbol: ${}^{110}_{47}\text{Ag}$ or Ag-110.

Row 2:
* Data: P=15, N=17, E=15
* Name: Atomic number 15 is Phosphorus (P).
* Ion Check: 15 protons vs 15 electrons. Equal. Neutral.
* Symbol: Mass = $15 + 17 = 32$. Symbol: ${}^{32}_{15}\text{P}$ or P-32.

Row 3:
* Data: P=12, N=12, E=12
* Name: Atomic number 12 is Magnesium (Mg).
* Ion Check: 12 protons vs 12 electrons. Equal. Neutral.
* Symbol: Mass = $12 + 12 = 24$. Symbol: ${}^{24}_{12}\text{Mg}$ or Mg-24.

Row 4:
* Data: P=12, N=13, E=12
* Name: Atomic number 12 is Magnesium (Mg).
* Ion Check: 12 protons vs 12 electrons. Equal. Neutral.
* Note: This is an isotope of the previous row (different neutron count).
* Symbol: Mass = $12 + 13 = 25$. Symbol: ${}^{25}_{12}\text{Mg}$ or Mg-25.

Row 5:
* Data: P=28, N=32, E=27
* Name: Atomic number 28 is Nickel (Ni).
* Ion Check: 28 protons (+) vs 27 electrons (-). There is one more positive charge. Charge is $+1$.
* Symbol: Mass = $28 + 32 = 60$. Symbol: ${}^{60}_{28}\text{Ni}^{+1}$ or Ni-60 (+1 charge).

Final Answer:
Fill in the blanks:
1. protons, neutrons (or nucleus)
2. protons
3. protons
4. protons and electrons

Multiple Choice:
5. c) nucleus
6. d) ion
7. b) neutral atom
8. b) different number of neutrons
9. c) carbon-14

Table Data:

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