Read the text and answer the questions.

Chlorine is a chemical element with symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine is a yellow-green gas at room temperature. It is an extremely reactive element and a strong oxidising agent: among the elements, it has the highest electron affinity and the third-highest electronegativity, behind only oxygen and fluorine.

The most common compound of chlorine, sodium chloride (common salt), has been known since ancient times. Around 1630, chlorine gas was first synthesised in a chemical reaction, but not recognised as a fundamentally important substance. Carl Wilhelm Scheele wrote a description of chlorine gas in 1774, supposing it to be an oxide of a new element. In 1809, chemists suggested that the gas might be a pure element, and this was confirmed by Sir Humphry Davy in 1810, who named it from based on its colour.

Because of its great reactivity, all chlorine in the Earth's crust is in the form of ionic chloride compounds, which includes table salt. It is the second-most abundant halogen (after fluorine) and twenty-first most abundant chemical element in Earth's crust. These crustal deposits are nevertheless dwarfed by the huge reserves of chloride in seawater.

1. What is this about?
2. What is that?
3. What is it represented by?
4. Is there a specific number?
5. What is it?
6. What color is it?
7. What state is it?
8. Is it non-reactive?
9. What does it have the highest of?
10. And ranks at number three as?
11. Where is it usually found?
12. When was it first written about?
13. By whom?
14. What did he say it was?
15. Who later spoke of it?
16. When?
17. Is it found in the ocean?
18. In small quantities?
19. What ranking is it, in common-ness?
20. Do we consume it?

Numbered answers:
1. Chlorine
2. a chemical element
3. symbol Cl
4. yes
5. 17
6. yellow-green
7. gas
8. no
9. electron affinity
10. electronegativity
11. unknown
12. in 1774
13. Carl Wilhelm Scheele
14. an oxide of a new element
15. Sir Humphry Davy
16. 1810
17. yes
18. no
19. unknown
20. yes