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# Unit 5: Periodic classification of elements

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## About this unit

Learn how the periodic table organizes the known elements of our world. In this unit, we will learn about the history of the periodic classification of elements, Mendeleev's periodic law, its merits and demerits. We will also learn about the modern periodic law, groups and periods, periodic trends - valence electrons, valency, atomic size, metallic, nonmetallic, electropositive, and electronegative characters.

### Practice

- Dobereiner's triadsGet 3 of 4 questions to level up!
- Periodic classification: Identify the lawsGet 3 of 4 questions to level up!

### Learn

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### Practice

- Electronic configuration of elements: KLMN shells.Get 3 of 4 questions to level up!
- Find the valence electronsGet 3 of 4 questions to level up!
- Identify elements with similar chemical propertiesGet 3 of 4 questions to level up!

Level up on the above skills and collect up to 400 Mastery points

### Practice

- Find the group and period of an elementGet 3 of 4 questions to level up!
- Groups and periods: find the atomic numberGet 3 of 4 questions to level up!
- Identify the elements belonging to the same group or periodGet 3 of 4 questions to level up!

Level up on the above skills and collect up to 240 Mastery points

### Learn

### Practice

- Find the valency of an elementGet 3 of 4 questions to level up!
- Valency: Write the formula of a compoundGet 3 of 4 questions to level up!
- Periodic trends of atomic sizeGet 5 of 7 questions to level up!

Level up on the above skills and collect up to 240 Mastery points

### Learn

### Practice

- Identify metals and nonmetals in the periodic tableGet 3 of 4 questions to level up!
- Periodic trends: metallic, nonmetallic, electropositive, & electronegative charactersGet 5 of 7 questions to level up!
- Formula of ionic and covalent compoundsGet 3 of 4 questions to level up!

Level up on the above skills and collect up to 240 Mastery points

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Level up on all the skills in this unit and collect up to 1,400 Mastery points!