Free Printable Atomic Structure Worksheets - Free Printable

Let’s go step by step to solve each part of this worksheet.

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Part 1: Label the parts of an atom and answer charge questions

First, look at the diagram (even though we can’t see it, we know what a basic atom looks like):

- The center is the nucleus, which contains protons and neutrons.
- Around the nucleus are electrons moving in orbits or shells.

So for labeling:
- The dots orbiting the center → Electron
- The particles inside the center with “+” signs → Proton
- The particles inside the center with no sign (or neutral) → Neutron

Now answer the questions:

a) Proton has a positive charge.
b) Neutron has no charge (neutral).
c) Electron has a negative charge.
d) The two particles in the nucleus are protons and neutrons.

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Part 2: Fill in protons, neutrons, electrons using element boxes

Remember these rules:
- Atomic Number = Number of Protons = Number of Electrons (in a neutral atom)
- Mass Number ≈ Average Atomic Mass rounded to nearest whole number
- Number of Neutrons = Mass Number – Atomic Number

Let’s do each element:

Carbon (C)
Atomic Number = 6 → #P = 6, #E = 6
Average atomic mass = 12.011 → round to 12 → Mass Number = 12
#N = 12 – 6 = 6

→ #P = 6, #N = 6, #E = 6

Neon (Ne)
Atomic Number = 10 → #P = 10, #E = 10
Average atomic mass = 20.108 → round to 20 → Mass Number = 20
#N = 20 – 10 = 10

→ #P = 10, #N = 10, #E = 10

Potassium (K)
Atomic Number = 19 → #P = 19, #E = 19
Average atomic mass = 39.098 → round to 39 → Mass Number = 39
#N = 39 – 19 = 20

→ #P = 19, #N = 20, #E = 19

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Part 3: Complete the table using periodic table knowledge

We’ll fill row by row. Remember:

- Atomic Number = #Protons = #Electrons (if neutral)
- Mass Number = #Protons + #Neutrons
- Symbol comes from periodic table based on atomic number

Row 1: Na (Sodium)
Given: #Protons = 11, #Neutrons = 12
→ Atomic Number = 11
→ Mass Number = 11 + 12 = 23
→ #Electrons = 11 (same as protons)

Row 2: K (Potassium)
Given: Mass Number = 39, #Electrons = 19
→ #Protons = 19 (since electrons = protons in neutral atom)
→ Atomic Number = 19
→ #Neutrons = 39 – 19 = 20

Row 3: ?
Given: #Protons = 38, #Neutrons = 50
→ Atomic Number = 38 → Element is Strontium (Sr)
→ Mass Number = 38 + 50 = 88
→ #Electrons = 38

Row 4: F (Fluorine)
Given: #Electrons = 9, #Neutrons = 10
→ #Protons = 9 → Atomic Number = 9
→ Mass Number = 9 + 10 = 19

Row 5: ?
Given: Atomic Number = 20, Mass Number = 40, #Electrons = 20
→ #Protons = 20 → Element is Calcium (Ca)
→ #Neutrons = 40 – 20 = 20

Row 6: ?
Given: Atomic Number = 50, #Electrons = 50, #Neutrons = 69
→ #Protons = 50 → Element is Tin (Sn)
→ Mass Number = 50 + 69 = 119

Row 7: I (Iodine)
Given: Atomic Number = 53, Mass Number = 127
→ #Protons = 53, #Electrons = 53
→ #Neutrons = 127 – 53 = 74

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Final Answer:

Part 1:
a) Positive
b) No charge (neutral)
c) Negative
d) Protons and neutrons

Part 2:
Carbon: #P = 6, #N = 6, #E = 6
Neon: #P = 10, #N = 10, #E = 10
Potassium: #P = 19, #N = 20, #E = 19

Part 3 Table:

| Symbol | Atomic Number | Mass Number | Number of Protons | Number of Electrons | Number of Neutrons |
|--------|---------------|-------------|-------------------|---------------------|--------------------|
| Na | 11 | 23 | 11 | 11 | 12 |
| K | 19 | 39 | 19 | 19 | 20 |
| Sr | 38 | 88 | 38 | 38 | 50 |
| F | 9 | 19 | 9 | 9 | 10 |
| Ca | 20 | 40 | 20 | 20 | 20 |
| Sn | 50 | 119 | 50 | 50 | 69 |
| I | 53 | 127 | 53 | 53 | 74 |