Printable worksheet for learning atomic structure, covering particles, charges, atomic number, and isotopes.

Here is the complete solution to the Atomic Structure Worksheet, with clear explanations for each question.

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1. Name the three particles of the atom and their respective charges.

| Particle | Charge type | Charge |
|-----------|-----------------|-------------|
| Proton | Positive | +1 |
| Neutron | Neutral | 0 |
| Electron | Negative | -1 |

> Explanation: Atoms are made of three subatomic particles:
> - Protons are positively charged and located in the nucleus.
> - Neutrons have no charge (neutral) and are also in the nucleus.
> - Electrons are negatively charged and orbit the nucleus in electron shells.

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2. The nucleus has a _positive_ charge and consists of _protons_ and _neutrons_.

> Explanation: The nucleus contains protons (+) and neutrons (0), so its overall charge is positive due to the protons. Electrons (-) orbit outside the nucleus.

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3. Electrons are located in the _electron cloud/orbitals/shells_ of an atom and carry _negative_ charge.

> Explanation: Electrons are found in regions around the nucleus called electron shells or orbitals. They have a negative charge, which balances the positive charge of the protons in a neutral atom.

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4. The number of protons in one atom of an element determines the atom’s _identity/element type_, and the number of electrons determines _chemical behavior/reactivity_ of an element.

> Explanation:
> - The number of protons = atomic number, which defines the element (e.g., 6 protons = carbon).
> - The number of electrons (especially valence electrons) determines how an atom bonds and reacts chemically.

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5. The atomic number tells you the number of _protons_ in one atom of an element. It also tells you the number of _electrons_ in a neutral atom of that element. The atomic number gives the “identity” of an element as well as its location on the Periodic Table. No two different elements will have the _same_ atomic number.

> Explanation:
> - Atomic number = # of protons.
> - In a neutral atom: # of protons = # of electrons.
> - Each element has a unique atomic number — this is what makes elements distinct.

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6. Give the symbol and number of protons in one atom of:

| Element | Symbol | Protons (Atomic Number) |
|--------------|--------|--------------------------|
| Beryllium | Be | 4 |
| Fluorine | F | 9 |
| Magnesium | Mg | 12 |
| Sulfur | S | 16 |
| Cobalt | Co | 27 |
| Tin | Sn | 50 |
| Arsenic | As | 33 |
| Gold | Au | 79 |

> Explanation: The number of protons = atomic number. You can find these on the periodic table.

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7. Give the symbol and number of electrons in a neutral atom of:

| Element | Symbol | Electrons (in neutral atom) |
|--------------|--------|------------------------------|
| Potassium | K | 19 |
| Argon | Ar | 18 |
| Calcium | Ca | 20 |
| Chromium | Cr | 24 |
| Cadmium | Cd | 48 |
| Lead | Pb | 82 |

> Explanation: In a neutral atom, electrons = protons = atomic number.

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8. Give the isotope symbol and number of neutrons in one atom of the following elements. Show your calculations.

> Formula:
> Number of neutrons = Mass number – Atomic number
> Isotope symbol: ^{mass number}ElementSymbol → e.g., ¹³³Cs

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#### Cesium – 133
- Atomic number of Cs = 55
- Neutrons = 133 – 55 = 78
- Isotope symbol: ¹³³Cs

#### Iron – 54
- Atomic number of Fe = 26
- Neutrons = 54 – 26 = 28
- Isotope symbol: ⁵⁴Fe

#### Ruthenium – 106
- Atomic number of Ru = 44
- Neutrons = 106 – 44 = 62
- Isotope symbol: ¹⁰⁶Ru

#### Nickel – 58
- Atomic number of Ni = 28
- Neutrons = 58 – 28 = 30
- Isotope symbol: ⁵⁸Ni

#### Polonium – 209
- Atomic number of Po = 84
- Neutrons = 209 – 84 = 125
- Isotope symbol: ²⁰⁹Po

#### Iodine – 135
- Atomic number of I = 53
- Neutrons = 135 – 53 = 82
- Isotope symbol: ¹³⁵I

#### Indium – 115
- Atomic number of In = 49
- Neutrons = 115 – 49 = 66
- Isotope symbol: ¹¹⁵In

#### Phosphorous – 31
- Atomic number of P = 15
- Neutrons = 31 – 15 = 16
- Isotope symbol: ³¹P

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✔ All questions answered with explanations and calculations.

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