Year 8 Science · Unit 2 · Lesson 07
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Learning Goals
Atomic data table
The first two rows are completed as examples. Use your knowledge of atomic number and mass number to fill in the remaining cells for sodium and iron.
| Element | Symbol | Atomic number (Z) | Mass number (A) | Protons | Neutrons | Electrons |
|---|---|---|---|---|---|---|
| Hydrogen-1 | ¹H | 1 | 1 | 1 | 0 | 1 |
| Carbon-12 | ¹²C | 6 | 12 | 6 | 6 | 6 |
| Sodium-23 | ²³Na | 23 | ||||
| Iron-56 | ⁵⁶Fe | 56 |
(a) Which of the four elements in the table has the most protons?
(b) Which element has the most neutrons? Show how you calculated this.
(c) In every row, the number of protons equals the number of electrons. Explain why this must be true for any neutral atom.
Scenario
A mystery atom has an atomic number of 17 and a mass number of 35. A student looks at the periodic table and says: "This atom must be chlorine, and it must have more neutrons than protons." The student makes both claims based on a single calculation.
(a) Predict whether the student is correct about both claims. Write your prediction clearly.
(b) Justify your prediction. Calculate the number of protons and neutrons and use these values to confirm or correct each of the student's claims.
1. An atom has 11 protons and 12 neutrons. Write the nuclear symbol for this atom, state its atomic number and mass number, and identify the element.
2. A student says: "If two atoms have the same mass number, they must be the same element." Do you agree? Use the concepts of atomic number and mass number to explain your answer.
Wrap Up
In one sentence, what was the main idea of this lesson?