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

Here is the completed Basic Atomic Structure Worksheet with 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: Atoms are made of three subatomic particles: protons (positively charged, in nucleus), neutrons (no charge, in nucleus), and electrons (negatively charged, orbiting nucleus).

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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 number of protons (atomic number) defines which element it is. The number of electrons (in a neutral atom = protons) 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 based on the masses and natural abundances of all isotopes of that element.

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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 refers to a specific isotope, not the average like atomic mass.

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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: Neutrons = Mass Number – Atomic Number

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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, found on the periodic table. Symbols are standard chemical abbreviations.

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

| Element | Symbol | Electrons (in neutral atom) |
|------------|--------|------------------------------|
| Uranium | U | 92 |
| Boron | B | 5 |
| Chlorine | Cl | 17 |
| Iodine | I | 53 |
| Xenon | Xe | 54 |

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

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

*(Mass numbers are ALWAYS whole numbers…show your calculations)*

We use:
Neutrons = Mass Number – Atomic Number

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

> Note: Mass numbers used are for the most abundant or stable isotopes. For example:
> - Hydrogen-1 (protium) has 0 neutrons.
> - Carbon-12 is the most common isotope.
> - Mercury’s most abundant isotope is Hg-202, but Hg-201 is also very common; we used 201 here for consistency with common textbook values. Some sources may use 202 → 202 – 80 = 122 neutrons. Always check if a specific isotope is given.

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✔ All questions answered with clear explanations and calculations where needed. Let me know if you’d like this formatted as a printable worksheet!