Basic Atomic Structure Worksheet - Staff.fcps.net - Free Printable

Here's the completed Basic Atomic Structure Worksheet with clear explanations for each answer.

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1. The 3 particles of the atom are:

a. Proton
b. Neutron
c. Electron

Their respective charges are:
a. +1 (positive)
b. 0 (neutral)
c. –1 (negative)

> 💡 *Explanation:* Protons are positively charged and located in the nucleus. Neutrons have no charge and also reside in the nucleus. Electrons are negatively charged and orbit the nucleus in electron shells.*

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2. The number of protons in one atom of an element determines the atom’s _identity_ and the number of electrons determines the _chemical behavior_ of the element.

> 💡 *Explanation:* The proton count (atomic number) defines what element it is (e.g., 6 protons = carbon). The number of electrons (especially valence electrons) determines how the atom bonds and reacts chemically.*

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3. 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 = proton count. In neutral atoms, protons = electrons. Each element has a unique atomic number — this is why the periodic table is ordered by atomic number.*

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4. The _atomic mass_ of an element is the average mass of an element’s naturally occurring atom, or isotopes, taking into account the _abundance_ of each isotope.

> 💡 *Explanation:* Atomic mass (or atomic weight) is a weighted average of all naturally occurring isotopes based on their percent abundance. For example, chlorine’s atomic mass is ~35.45 because it’s a mix of Cl-35 and Cl-37.*

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5. The _mass number_ of an element is the total number of protons and neutrons in the _nucleus_ of the atom.

> 💡 *Explanation:* Mass number = protons + neutrons. It’s specific to a particular isotope. For example, carbon-12 has mass number 12 (6p + 6n).*

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6. The mass number is used to calculate the number of _neutrons_ in one atom of an element. In order to calculate the number of neutrons you must subtract the _atomic number_ from the _mass number_.

> 💡 *Formula:*
> Number of neutrons = Mass number – Atomic number
> Example: Oxygen-16 → 16 – 8 = 8 neutrons.

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

| Element | Symbol | Protons (Atomic Number) |
|-----------|--------|--------------------------|
| Lithium | Li | 3 |
| Iron | Fe | 26 |
| Oxygen | O | 8 |
| Krypton | Kr | 36 |
| Bromine | Br | 35 |
| Copper | Cu | 29 |
| Mercury | Hg | 80 |
| Helium | He | 2 |

> 💡 *Explanation:* The number of protons = atomic number, which you can find on the periodic table. Symbols are standard abbreviations.*

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

*(In a neutral atom, # electrons = # protons)*

| Element | Symbol | Electrons (Same as protons) |
|-----------|--------|------------------------------|
| Uranium | U | 92 |
| Boron | B | 5 |
| Chlorine | Cl | 17 |
| Iodine | I | 53 |
| Xenon | Xe | 54 |

> 💡 *Explanation:* Neutral atoms have equal numbers of protons and electrons. So just use the atomic number.*

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9. Give the symbol of and the number of neutrons in one atom of:

*(Mass number – Atomic number = Neutrons. Use most common isotope unless specified.)*

| Element | Symbol | Mass Number (most common isotope) | Atomic Number | Neutrons (Calculation) |
|-------------|--------|-----------------------------------|---------------|-------------------------|
| Barium | Ba | 137 | 56 | 137 – 56 = 81 |
| Carbon | C | 12 | 6 | 12 – 6 = 6 |
| Fluorine | F | 19 | 9 | 19 – 9 = 10 |
| Europium | Eu | 152 | 63 | 152 – 63 = 89 |
| Bismuth | Bi | 209 | 83 | 209 – 83 = 126 |
| Hydrogen | H | 1 | 1 | 1 – 1 = 0 |
| Magnesium | Mg | 24 | 12 | 24 – 12 = 12 |
| Mercury | Hg | 201 | 80 | 201 – 80 = 121 |

> 💡 *Note:* These calculations assume the most abundant stable isotope. For hydrogen, the most common isotope (protium) has 0 neutrons. Some elements like europium and bismuth have only one stable isotope, so those values are fixed.

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✔ Final Tips:
- Always refer to the periodic table for atomic numbers.
- Mass number is usually rounded to the nearest whole number for these types of problems.
- Remember: Neutral atom ⇒ electrons = protons

Let me know if you’d like a printable version or further clarification!