Free Printable Protons Neutrons and Electrons Practice Worksheets - Free Printable

Here are the solutions to your worksheet. I have worked through each problem step-by-step to ensure the numbers are correct.

1. Using the periodic table, fill in the blanks.

To fill this table, we use three main rules:
* Protons: This is the Atomic Number (found on the periodic table). It identifies the element.
* Electrons: In a neutral atom, electrons equal protons.
* Neutrons: Subtract Protons from the Atomic Mass (Mass - Protons = Neutrons).
* Atomic Mass: Add Protons and Neutrons together.

Row 1: Hydrogen (H)
* Protons: 1 (Given)
* Electrons: 1 (Same as protons)
* Atomic Mass: The most common mass for Hydrogen is 1.
* Neutrons: $1 - 1 = 0$.

Row 2: Helium (He)
* Atomic Mass: 4 (Given)
* Protons: Helium is element #2, so it has 2 protons.
* Electrons: Same as protons, so 2.
* Neutrons: $4 - 2 = 2$.

Row 3: Carbon (C)
* Protons: 6 (Given). Element #6 is Carbon.
* Electrons: Same as protons, so 6.
* Atomic Mass: The most common mass for Carbon is 12.
* Neutrons: $12 - 6 = 6$.

Row 4: Nitrogen (N)
* Neutrons: 7 (Given).
* Protons: Nitrogen is element #7, so it has 7 protons.
* Electrons: Same as protons, so 7.
* Atomic Mass: $7 \text{ (protons)} + 7 \text{ (neutrons)} = 14$.

Row 5: Oxygen (O)
* Protons: Oxygen is element #8, so it has 8 protons.
* Electrons: Same as protons, so 8.
* Atomic Mass: The most common mass for Oxygen is 16.
* Neutrons: $16 - 8 = 8$.

Row 6: Sodium (Na)
* Protons: Sodium is element #11, so it has 11 protons.
* Electrons: Same as protons, so 11.
* Atomic Mass: The most common mass for Sodium is 23.
* Neutrons: $23 - 11 = 12$.

Row 7: Chlorine (Cl)
* Protons: Chlorine is element #17, so it has 17 protons.
* Electrons: Same as protons, so 17.
* Atomic Mass: The most common mass for Chlorine is 35.
* Neutrons: $35 - 17 = 18$.

Row 8: Iron (Fe)
* Protons: Iron is element #26, so it has 26 protons.
* Electrons: Same as protons, so 26.
* Atomic Mass: The most common mass for Iron is 56.
* Neutrons: $56 - 26 = 30$.

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2. Uranium-235 (U-235) atom consists of how many protons, neutrons, and electrons?

* Protons: Look up Uranium (U) on the periodic table. It is element number 92. So, it has 92 protons.
* Electrons: In a neutral atom, electrons equal protons. So, it has 92 electrons.
* Neutrons: The number "235" is the atomic mass. To find neutrons, subtract protons from the mass: $235 - 92 = 143$. So, it has 143 neutrons.

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3. Determine the atomic mass of an atom with 18 protons, 22 neutrons, and 18 electrons. What element is it?

* Identify the Element: The identity of an element is determined by the number of protons. The element with 18 protons is Argon (Ar).
* Calculate Atomic Mass: Add the protons and neutrons together.
$$18 \text{ (protons)} + 22 \text{ (neutrons)} = 40$$
The atomic mass is 40 amu.

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4. A Sodium-23 (Na-23) atom has how many protons, neutrons, and electrons?

* Protons: Sodium (Na) is element number 11 on the periodic table. So, it has 11 protons.
* Electrons: Equal to the number of protons. So, it has 11 electrons.
* Neutrons: The mass is 23. Subtract the protons: $23 - 11 = 12$. So, it has 12 neutrons.

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5. Calculate the number of protons, neutrons, and electrons in an atom of Aluminum-27 (Al-27).

* Protons: Aluminum (Al) is element number 13 on the periodic table. So, it has 13 protons.
* Electrons: Equal to the number of protons. So, it has 13 electrons.
* Neutrons: The mass is 27. Subtract the protons: $27 - 13 = 14$. So, it has 14 neutrons.

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Final Answer:

1. Table Completion:

| Element | Symbol | Protons | Neutrons | Electrons | Atomic Mass (amu) |
| :--- | :---: | :---: | :---: | :---: | :---: |
| Hydrogen | H | 1 | 0 | 1 | 1 |
| Helium | He | 2 | 2 | 2 | 4 |
| Carbon | C | 6 | 6 | 6 | 12 |
| Nitrogen | N | 7 | 7 | 7 | 14 |
| Oxygen | O | 8 | 8 | 8 | 16 |
| Sodium | Na | 11 | 12 | 11 | 23 |
| Chlorine | Cl | 17 | 18 | 17 | 35 |
| Iron | Fe | 26 | 30 | 26 | 56 |

*(Note: Atomic masses listed are based on the most common isotopes found in nature).*

2. Uranium-235:
* Protons: 92
* Neutrons: 143
* Electrons: 92

3. Unknown Atom:
* Atomic Mass: 40 amu
* Element: Argon (Ar)

4. Sodium-23:
* Protons: 11
* Neutrons: 12
* Electrons: 11

5. Aluminum-27:
* Protons: 13
* Neutrons: 14
* Electrons: 13