Atomic Structure Worksheet: Basic - Free Printable

Let’s work through the worksheet step by step.

---

Part 1: Fill in the blanks about atomic structure

1. The Atomic Number is the number of protons and electrons in an atom.
→ *Why?* In a neutral atom, protons (positive) equal electrons (negative), so the atomic number tells you both.

2. The Atomic Mass is the number of protons and neutrons in the nucleus of an atom.
→ *Why?* Electrons are too light to count toward mass — only protons and neutrons matter for atomic mass.

3. Where is the majority of the mass located in an atom?
→ In the nucleus (where protons and neutrons are).

---

Part 2: Fill in the blanks for each element

We’ll go one by one. Remember:

- Atomic # = number of protons
- In a neutral atom, # of electrons = # of protons
- Atomic Mass ≈ rounded whole number (from periodic table)
- # of Neutrons = Atomic Mass (rounded) – Atomic #

---

Element 4: Hydrogen (H)
Atomic # = 1
Atomic Mass = 1.008 → round to 1
# of Protons = 1
# of Neutrons = 1 - 1 = 0
# of Electrons = 1 (same as protons in neutral atom)

✔ Answer:
Atomic # = 1
Atomic Mass # = 1
# of Protons = 1
# of Neutrons = 0
# of Electrons = 1

---

Element 5: Helium (He)
Atomic # = 2
Atomic Mass = 4.0026 → round to 4
# of Protons = 2
# of Neutrons = 4 - 2 = 2
# of Electrons = 2

✔ Answer:
Atomic # = 2
Atomic Mass # = 4
# of Protons = 2
# of Neutrons = 2
# of Electrons = 2

---

Element 6: Boron (B)
Atomic # = 5
Atomic Mass = 10.81 → round to 11
# of Protons = 5
# of Neutrons = 11 - 5 = 6
# of Electrons = 5

✔ Answer:
Atomic # = 5
Atomic Mass # = 11
# of Protons = 5
# of Neutrons = 6
# of Electrons = 5

---

Element 7: Nitrogen (N)
Atomic # = 7
Atomic Mass = 14.007 → round to 14
# of Protons = 7
# of Neutrons = 14 - 7 = 7
# of Electrons = 7

✔ Answer:
Atomic # = 7
Atomic Mass # = 14
# of Protons = 7
# of Neutrons = 7
# of Electrons = 7

---

Element 8: Rubidium (Rb)
Atomic # = 37
Atomic Mass = 85.468 → round to 85
# of Protons = 37
# of Neutrons = 85 - 37 = 48
# of Electrons = 37

✔ Answer:
Atomic # = 37
Atomic Mass # = 85
# of Protons = 37
# of Neutrons = 48
# of Electrons = 37

---

Element 9: Ruthenium (Ru)
Atomic # = 44
Atomic Mass = 101.07 → round to 101
# of Protons = 44
# of Neutrons = 101 - 44 = 57
# of Electrons = 44

✔ Answer:
Atomic # = 44
Atomic Mass # = 101
# of Protons = 44
# of Neutrons = 57
# of Electrons = 44

---

Element 10: Xenon (Xe)
Atomic # = 54
Atomic Mass = 131.29 → round to 131
# of Protons = 54
# of Neutrons = 131 - 54 = 77
# of Electrons = 54

✔ Answer:
Atomic # = 54
Atomic Mass # = 131
# of Protons = 54
# of Neutrons = 77
# of Electrons = 54

---

Element 11: Gold (Au)
Atomic # = 79
Atomic Mass = 196.97 → round to 197
# of Protons = 79
# of Neutrons = 197 - 79 = 118
# of Electrons = 79

✔ Answer:
Atomic # = 79
Atomic Mass # = 197
# of Protons = 79
# of Neutrons = 118
# of Electrons = 79

---

Final Answer:
1. protons, electrons
2. protons, neutrons
3. nucleus
4. Atomic # = 1, Atomic Mass # = 1, # of Protons = 1, # of Neutrons = 0, # of Electrons = 1
5. Atomic # = 2, Atomic Mass # = 4, # of Protons = 2, # of Neutrons = 2, # of Electrons = 2
6. Atomic # = 5, Atomic Mass # = 11, # of Protons = 5, # of Neutrons = 6, # of Electrons = 5
7. Atomic # = 7, Atomic Mass # = 14, # of Protons = 7, # of Neutrons = 7, # of Electrons = 7
8. Atomic # = 37, Atomic Mass # = 85, # of Protons = 37, # of Neutrons = 48, # of Electrons = 37
9. Atomic # = 44, Atomic Mass # = 101, # of Protons = 44, # of Neutrons = 57, # of Electrons = 44
10. Atomic # = 54, Atomic Mass # = 131, # of Protons = 54, # of Neutrons = 77, # of Electrons = 54
11. Atomic # = 79, Atomic Mass # = 197, # of Protons = 79, # of Neutrons = 118, # of Electrons = 79