CORE Chemistry (Short Course) - 9222 OxfordAQA

Group Properties

Akopọ

In a school preparation room there is a jar of soft grey metal sitting under a layer of oil, and the oil is not there to keep it clean. It is there because the metal cannot be left alone with the air, let alone with water. Cut a piece with a knife and the fresh surface is bright for a second or two before it dulls. Drop that piece into a trough and it floats, because it is lighter than the water it is busy attacking. Almost nothing else on the chart behaves like that, and the reason is written into where the metal sits.

This lesson is about one column of the periodic table and what changes as you travel down it. The reaction with water goes from a steady fizz at the top to something no school would attempt at the bottom, and the escalation is completely regular. One sentence about outer electrons explains the whole of it. Along the way you will learn to predict the behaviour of elements too reactive to be handed to you in a bottle, and to turn a table of measurements into a statement an examiner will pay for.

Awọn Afojusun

  1. The elements in Group 1 of the periodic table (known as the alkali metals): are metals with low density (the first three elements in the group are less dense than water); react with non-metals to form ionic compounds in which the metal ion carries a charge of +1. The compounds are white solids that dissolve in water to form colourless solutions; react with water, releasing hydrogen; form hydroxides that dissolve in water to give alkaline solutions.
  2. In Group 1, the further down the group an element is, the more reactive the element.
  3. The trends in reactivity within groups in the periodic table can be explained because the higher the energy level of the outer electrons: the more easily electrons are lost Students should be able to explain the relative reactivities of the elements in Group 1.

Àwòrán ọpọlọ

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Akọ̀wé Ẹ̀kọ́

Drop a lentil-sized piece of lithium into a trough of water and it bobs on the surface, fizzing quietly, gradually getting smaller. Repeat the experiment with sodium and the metal melts into a silver bead that skates around leaving a trail. Do it with potassium and the hydrogen coming off catches fire, burning with a lilac flame, and the bead sometimes leaves the trough altogether. Three elements, one column of the chart, one reaction, and an unmistakable escalation as you move down.

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Ìdánwò Ẹ̀kọ́

Oriire fun ipari ẹkọ lori Group Properties. Ni bayi ti o ti ṣawari naa awọn imọran bọtini ati awọn imọran, o to akoko lati fi imọ rẹ si idanwo. Ẹka yii nfunni ni ọpọlọpọ awọn adaṣe awọn ibeere ti a ṣe lati fun oye rẹ lokun ati ṣe iranlọwọ fun ọ lati ṣe iwọn oye ohun elo naa.

Iwọ yoo pade adalu awọn iru ibeere, pẹlu awọn ibeere olumulo pupọ, awọn ibeere idahun kukuru, ati awọn ibeere iwe kikọ. Gbogbo ibeere kọọkan ni a ṣe pẹlu iṣaro lati ṣe ayẹwo awọn ẹya oriṣiriṣi ti imọ rẹ ati awọn ogbon ironu pataki.

Lo ise abala yii gege bi anfaani lati mu oye re lori koko-ọrọ naa lagbara ati lati ṣe idanimọ eyikeyi agbegbe ti o le nilo afikun ikẹkọ. Maṣe jẹ ki awọn italaya eyikeyi ti o ba pade da ọ lójú; dipo, wo wọn gẹgẹ bi awọn anfaani fun idagbasoke ati ilọsiwaju.

  1. Which statement about the elements of Group 1 is correct? A. They form ions with a charge of -1. B. They become less reactive going down the group. C. They react with water to release hydrogen. D. Their compounds are coloured solids. Answer: C
  2. Lithium, sodium and potassium all float when added to water. This is because they: A. have a density less than that of water B. have low melting points C. are held up by the hydrogen produced D. do not dissolve in water Answer: A
  3. Sodium is added to water containing universal indicator. Which pair of products is formed? A. Sodium oxide and hydrogen B. Sodium hydroxide and oxygen C. Sodium hydroxide and hydrogen D. Sodium hydride and oxygen Answer: C
  4. A piece of rubidium is added to cold water. Compared with potassium, the reaction is expected to be: A. slower, because rubidium atoms are heavier B. slower, because rubidium has more electron shielding C. more vigorous, because the outer electron is lost more easily D. identical, because both metals are in Group 1 Answer: C
  5. Why is potassium more reactive than sodium? A. A potassium atom has more outer electrons than a sodium atom. B. A potassium atom has a lower density than a sodium atom. C. The outer electron of potassium is in a higher energy level and is lost more easily. D. A potassium atom gains an electron more easily than a sodium atom. Answer: C

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