Valence Electrons and Ions Worksheet Answer Key Form - Fill Out ... - Free Printable

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I’ll solve each question based on standard chemistry knowledge. Let’s go question by question:

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1. What is a valence electron and why are they important to a chemist?

> Answer:
A valence electron is an electron in the outermost shell (highest energy level) of an atom. These electrons are involved in forming chemical bonds with other atoms. They are important to chemists because they determine an element’s chemical properties, reactivity, and how it bonds with other elements (ionic, covalent, metallic).

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2. What is the periodic trend for finding the number of valence electrons when looking at the periodic table?

> Answer:
For main group elements (Groups 1–2 and 13–18), the number of valence electrons corresponds to the group number:
- Group 1 → 1 valence electron
- Group 2 → 2 valence electrons
- Group 13 → 3
- Group 14 → 4
- Group 15 → 5
- Group 16 → 6
- Group 17 → 7
- Group 18 → 8 (except Helium, which has 2)

*Note: Transition metals (Groups 3–12) don’t follow this simple pattern and often have variable valence electrons.*

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3. How many valence electrons are there in an atom of oxygen? ___ Ba²⁺ ___ K⁺?

> Answer:
- Oxygen (O) → Group 16 → 6 valence electrons
- Ba²⁺ (Barium ion) → Barium is in Group 2; loses 2 electrons to form Ba²⁺ → 0 valence electrons (its outer shell is now empty, like noble gas configuration)
- K⁺ (Potassium ion) → Potassium is in Group 1; loses 1 electron to form K⁺ → 0 valence electrons (also achieves noble gas configuration)

✔ So:
Oxygen: 6
Ba²⁺: 0
K⁺: 0

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4. Valence electrons can be shown using Lewis dot structures. Draw the Lewis dot structure for: a. calcium b. sodium c. strontium

> Answer:
Lewis dot structures show valence electrons as dots around the element symbol.

- Calcium (Ca) – Group 2 → 2 valence electrons
`Ca` with two dots (usually one on each side, or both on one side — doesn’t matter as long as total = 2)

- Sodium (Na) – Group 1 → 1 valence electron
`Na` with one dot

- Strontium (Sr) – Group 2 → 2 valence electrons
`Sr` with two dots

*(In text, we can represent them as:)*
a. Ca: •Ca•
b. Na: Na•
c. Sr: •Sr•

*(Note: In actual drawings, dots are placed on the four sides of the symbol — top, right, bottom, left — and paired only after each side has one dot.)*

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5. Elements that are classified as metals or nonmetals tend to form cations (positive ions) or anions (negative ions).

> Answer:
- Metals → tend to lose electrons → form cations (positive ions)
- Nonmetals → tend to gain electrons → form anions (negative ions)

So fill in:
Metals → cations
Nonmetals → anions

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6. A cation ________ electrons causing the ion to have a __________ charge.

> Answer:
A cation loses electrons causing the ion to have a positive charge.

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7. An anion ________ electrons causing the ion to have a __________ charge.

> Answer:
An anion gains electrons causing the ion to have a negative charge.

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8. What does a roman numeral tell you when it is written after an element name?

> Answer:
A Roman numeral indicates the charge (oxidation state) of a transition metal ion that can have multiple possible charges. For example:
- Iron(II) = Fe²⁺
- Iron(III) = Fe³⁺
- Copper(I) = Cu⁺
- Copper(II) = Cu²⁺

This helps distinguish between different ionic forms of the same metal.

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9. Write the symbols and charges for the following ions. Also classify as metal/nonmetal and cation/anion.

> Answer:

| Element | Symbol & Charge | Metal or Nonmetal? | Cation or Anion? |
|---------------|------------------|--------------------|------------------|
| Calcium | Ca²⁺ | Metal | Cation |
| Bromine | Br⁻ | Nonmetal | Anion |
| Nitrogen | N³⁻ | Nonmetal | Anion |
| Oxygen | O²⁻ | Nonmetal | Anion |
| Tin(IV) | Sn⁴⁺ | Metal | Cation |
| Fluorine | F⁻ | Nonmetal | Anion |
| Selenium | Se²⁻ | Nonmetal | Anion |
| Sodium | Na⁺ | Metal | Cation |
| Phosphorus | P³⁻ | Nonmetal | Anion |
| Copper(I) | Cu⁺ | Metal | Cation |
| Lithium | Li⁺ | Metal | Cation |
| Zinc | Zn²⁺ | Metal | Cation |
| Sulfur | S²⁻ | Nonmetal | Anion |
| Manganese(IV) | Mn⁴⁺ | Metal | Cation |
| Chlorine | Cl⁻ | Nonmetal | Anion |
| Oxygen | O²⁻ | Nonmetal | Anion |

*(Note: Oxygen appears twice — same answer both times.)*

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✔ Final Notes:

- This worksheet reinforces understanding of valence electrons, ion formation, Lewis structures, and naming conventions.
- Key concepts: Metals lose e⁻ → cations; nonmetals gain e⁻ → anions; Roman numerals = charge of transition metal ions.

Let me know if you’d like me to draw the Lewis structures visually (in ASCII art) or explain any part further!