The Periodic Table
Aperçu
Hanging on the wall of every chemistry laboratory is a chart that looks, at first glance, like a storage rack for about 118 facts. It is nothing of the sort. It is the most powerful prediction machine that chemistry has ever produced. Hand a chemist an element they have never worked with, tell them only where it sits on that chart, and they will tell you whether it is a metal, roughly how it will behave with water, and what the formula of its oxide is likely to be.
This lesson takes the chart apart and shows you the machinery. You will find out why the columns exist at all, what is actually repeating when we call the table periodic, how to read the four lines printed inside every box on the copy this course gives you, and how a professor in St Petersburg was able to describe elements that nobody had yet laid eyes on. You will finish with the strangest column of the lot: a little under one percent of the air you are breathing, made of atoms so content with their own electrons that for a century chemists believed they could form no compounds at all.
Objectifs
- The periodic table is arranged in order of atomic (proton) number. Elements with similar properties are in columns, known as groups. The table is called a periodic table because similar properties occur at regular intervals. Students should know that the current periodic table is based on the work of Mendeleev.
- Elements in the same group in the periodic table have the same number of electrons in their highest energy level (outer electrons) and this gives them similar chemical properties. Students should know that basing the periodic table on groups of elements with similar properties has allowed for the prediction of elements which were still to be discovered.
- The elements in Group 0 of the periodic table are called the noble gases. They are unreactive because their atoms have stable arrangements of electrons. Students should know that the noble gases have eight electrons in their outer energy level, except for helium, which has only two electrons.
Carte mentale
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Note de cours
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Évaluation de la leçon
Félicitations, vous avez terminé la leçon sur The Periodic Table. Maintenant que vous avez exploré le concepts et idées clés, il est temps de mettre vos connaissances à lépreuve. Cette section propose une variété de pratiques des questions conçues pour renforcer votre compréhension et vous aider à évaluer votre compréhension de la matière.
Vous rencontrerez un mélange de types de questions, y compris des questions à choix multiple, des questions à réponse courte et des questions de rédaction. Chaque question est soigneusement conçue pour évaluer différents aspects de vos connaissances et de vos compétences en pensée critique.
Utilisez cette section d'évaluation comme une occasion de renforcer votre compréhension du sujet et d'identifier les domaines où vous pourriez avoir besoin d'étudier davantage. Ne soyez pas découragé par les défis que vous rencontrez ; considérez-les plutôt comme des opportunités de croissance et d'amélioration.
- The elements in the modern periodic table are arranged in order of increasing: A. mass number B. atomic number C. number of neutrons D. relative atomic mass Answer: B
- An atom of an element has the electron arrangement 2,8,8,1. In which group of the periodic table is this element found? A. Group 0 B. Group 1 C. Group 2 D. Group 7 Answer: B
- Which statement must be true of two elements found in the same group? A. They have the same number of protons in their atoms. B. They have the same number of occupied energy levels. C. They have the same number of electrons in their highest occupied energy level. D. They have the same relative atomic mass. Answer: C
- Why are the elements in Group 0 unreactive? A. Their atoms are much smaller than other atoms. B. Their atoms already have a stable arrangement of electrons. C. Their atoms contain no electrons in the outer energy level. D. Their atoms have more neutrons than protons. Answer: B
- Which statement about the outer energy level of the noble gases is correct? A. Every noble gas has eight electrons in it. B. Every noble gas has two electrons in it. C. Helium has two electrons in it and the other noble gases have eight. D. Helium has eight electrons in it and the other noble gases have two. Answer: C
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