Uploaded February 2017 | Updated September 2026, 46 minutes ago

---

Mr. Key outlines the factors that contribute to observed trends in the periodic table, culminating in the prediction of the reactivity of elements.

Please note that all questions, comments and critiques are welcome. However, because the primary purpose of these videos is educational for students/educators, the comments are moderated. Any comments that are deemed abusive, inappropriate, or unrelated to the topic matter will not be posted and the user potentially blocked.