Let’s go step by step to solve Question 6.
We are asked to write a math equation that tells us the charge of an ion, using the number of protons and electrons in that ion. Then we need to test it with two positive ions and two negative ions from the table in Question 1.
First, remember:
- Protons have a +1 charge each.
- Electrons have a -1 charge each.
- The total charge of an ion = (total proton charge) + (total electron charge)
So if you have P protons and E electrons:
Charge = (+1 × P) + (-1 × E)
Which simplifies to:
Charge = P – E
That’s our equation!
Now let’s test it with examples from the table.
✔ Positive Ion Examples:
1. Lithium ion: Charge is 1+
From Model 1 (page 54 — not shown here, but standard knowledge):
Lithium atom has 3 protons. When it becomes Li⁺, it loses 1 electron → so it has 2 electrons.
Plug into equation: 3 – 2 = 1 → matches 1+ ✔️
2. Magnesium ion: Charge is 2+
Magnesium has 12 protons. Mg²⁺ has lost 2 electrons → 10 electrons.
Equation: 12 – 10 = 2 → matches 2+ ✔️
✔ Negative Ion Examples:
1. Fluorine ion: Charge is 1–
Fluorine has 9 protons. F⁻ gains 1 electron → 10 electrons.
Equation: 9 – 10 = -1 → matches 1– ✔️
2. Oxygen ion: Charge is 2–
Oxygen has 8 protons. O²⁻ gains 2 electrons → 10 electrons.
Equation: 8 – 10 = -2 → matches 2– ✔️
All four examples work!
Final Answer:
Number of protons – number of electrons = charge
Parent Tip: Review the logic above to help your child master the concept of positive and negative ions worksheet answer key.
