Atomic and Mass Number worksheet - Free Printable

To fill in this table, we need to look up each element on the Periodic Table. Here is how the numbers work:

1. Atomic Number: This is the big number usually at the top of the element's box. It tells you the identity of the element.
2. Number of Protons: This is always equal to the Atomic Number.
3. Number of Electrons: In a neutral atom (which these are), this is also equal to the Atomic Number.
4. Mass Number: This is usually the bigger number at the bottom of the element's box. Since it's often a decimal (like 22.99), we round it to the nearest whole number for this type of worksheet.
5. Number of Neutrons: To find this, subtract the Atomic Number from the Mass Number.
* *Formula:* Mass Number - Atomic Number = Neutrons.

Here is the step-by-step breakdown for each row:

* Sodium (Na): Atomic # is 11. Mass # rounds to 23. Neutrons: $23 - 11 = 12$.
* Beryllium (Be): Atomic # is 4. Mass # rounds to 9. Neutrons: $9 - 4 = 5$.
* Carbon (C): Atomic # is 6. Mass # rounds to 12. Neutrons: $12 - 6 = 6$.
* Lithium (Li): Atomic # is 3. Mass # rounds to 7. Neutrons: $7 - 3 = 4$.
* Oxygen (O): Atomic # is 8. Mass # rounds to 16. Neutrons: $16 - 8 = 8$.
* Sulfur (S): Atomic # is 16. Mass # rounds to 32. Neutrons: $32 - 16 = 16$.
* Cobalt (Co): Atomic # is 27. Mass # rounds to 59. Neutrons: $59 - 27 = 32$.
* Iron (Fe): Atomic # is 26. Mass # rounds to 56. Neutrons: $56 - 26 = 30$.
* Nitrogen (N): Atomic # is 7. Mass # rounds to 14. Neutrons: $14 - 7 = 7$.
* Sodium (Na): (Repeat) Atomic # is 11. Mass # is 23. Neutrons: 12.
* Rubidium (Rb): Atomic # is 37. Mass # rounds to 85. Neutrons: $85 - 37 = 48$.
* Silicon (Si): Atomic # is 14. Mass # rounds to 28. Neutrons: $28 - 14 = 14$.
* Aluminium (Al): Atomic # is 13. Mass # rounds to 27. Neutrons: $27 - 13 = 14$.
* Phosphorus (P): Atomic # is 15. Mass # rounds to 31. Neutrons: $31 - 15 = 16$.
* Nickel (Ni): Atomic # is 28. Mass # rounds to 59 (standard rounding). Neutrons: $59 - 28 = 31$.
* Copper (Cu): Atomic # is 29. Mass # rounds to 64. Neutrons: $64 - 29 = 35$.
* Zinc (Zn): Atomic # is 30. Mass # rounds to 65. Neutrons: $65 - 30 = 35$.
* Yttrium (Y): Atomic # is 39. Mass # rounds to 89. Neutrons: $89 - 39 = 50$.
* Boron (B): Atomic # is 5. Mass # rounds to 11. Neutrons: $11 - 5 = 6$.

Final Answer:

| Element | Atomic number | Mass number | Number of protons | Number of electrons | Number of neutrons |
| :--- | :---: | :---: | :---: | :---: | :---: |
| Sodium (Na) | 11 | 23 | 11 | 11 | 12 |
| Beryllium (Be) | 4 | 9 | 4 | 4 | 5 |
| Carbon (C) | 6 | 12 | 6 | 6 | 6 |
| Lithium (Li) | 3 | 7 | 3 | 3 | 4 |
| Oxygen (O) | 8 | 16 | 8 | 8 | 8 |
| Sulfur (S) | 16 | 32 | 16 | 16 | 16 |
| Cobalt (Co) | 27 | 59 | 27 | 27 | 32 |
| Iron (Fe) | 26 | 56 | 26 | 26 | 30 |
| Nitrogen (N) | 7 | 14 | 7 | 7 | 7 |
| Sodium (Na) | 11 | 23 | 11 | 11 | 12 |
| Rubidium (Rb) | 37 | 85 | 37 | 37 | 48 |
| Silicon (Si) | 14 | 28 | 14 | 14 | 14 |
| Aluminium (Al) | 13 | 27 | 13 | 13 | 14 |
| Phosphorus (P) | 15 | 31 | 15 | 15 | 16 |
| Nickel (Ni) | 28 | 59 | 28 | 28 | 31 |
| Copper (Cu) | 29 | 64 | 29 | 29 | 35 |
| Zinc (Zn) | 30 | 65 | 30 | 30 | 35 |
| Yttrium (Y) | 39 | 89 | 39 | 39 | 50 |
| Boron (B) | 5 | 11 | 5 | 5 | 6 |