Cho oxide cao nhất của nguyên tố R là R2O5, hợp chất kí của R với hydrogen chứa 17,64% khối lượng H.
a) Tìm tên R?
b) Viết CT oxide hợp chất khí? Gọi tên

Choose the correct form of the verbs in brackets:
1. I see that Tom (writes/is writing) his composition
2. He says that he (looks/will look) for a job next week
3. They think he (was/would be) here last night
4. He tells us that he (was/has been) to the mountains before
5. I hoped that he (will be/would be) able to attend
6. He wants to do it before his father (will come/comes)
7. People have said that the sun (rise) in the East
8. He says he (does/will do) it some time
9. He asked the guard what time the train usually (starts/started)
10. He told me in the morning that he (is going/was going) with us the following day
11. He says that he (finished/will finish) the project by May
12. I realized that they (are/were) older than they looked
13. I hear that Kate (accepted/has accepted) a new position
14. They told me they (have never seen/had never seen) her before
15. We know that you (move/will move) to France next year
16. In Britain, the weather is very varied. People (never know/have never known) what it (is/will be) like the next day
17. He (is/had been) ill for a long time before he died
18. She didn't tell me the reason why she (didn't come/hadn't come) to school the day before
19. I had no map, that's why I (got/get) lost
20. I hope it (doesn't rain/will not rain) when we start early tomorrow

Đề: Nếu bố mẹ phản đối việc bạn thần tượng ai thì bạn hãy viết thư trình bày quan điểm của mình (thần tượng của mình là thiên thần nha)

Nguyên tử X có tổng số hạt là 76, trong đó số hạt không mang điện nhiều hơn hạt mang điện dương là 4
a) Viết kí hiệu nguyên tử X
b) Xác định vị trí của X trong BTH? Giải thích?

Đường dây cao thế nối thẳng từ vị trí A đến vị trí B dài 10km, từ vị trí A đến vị trí C dài 8km, góc tạo bởi 2 đường dây bằng 75°. Khoảng cách từ vị trí B đến vị trí C xấp xỉ bằng bao nhiêu?

Giải bài này giùm tui với!!!

1) Sắp xếp các nguyên tử sau đây theo thứ tự tăng dần độ âm điện: Cl, Al, Na, P, F

2) Sắp xếp các nguyên tử sau đây theo thứ tự giảm dần tính kim loại: Na, AI, Si, Mg, P, Cl, S, F

Giải bài này giùm mình nha!

I. Put in at, on or in.
1. Mozart was born in Salzburg _____ 1756
2. I haven't seen Kate for a few days. I last saw her _____ Tuesday
3. The price of electricity is going up _____ October
4. I've been invited to the wedding _____ 14 February
5. Hurry up! We've got to go _____ five minutes
6. I'm busy now but I'll be with you _____ a moment
7. Jenny's brother is out of work _____ the moment
8. There are usually a lot of parties _____ New Year's Eve
9. I hope the weather will be nice _____ the weekend
10. _____ Saturday night I went to bed _____ 11 o'clock
11. I don't like travelling _____ night
12. We travelled overnight to Paris and arrived _____ 5 o'clock _____ the morning
13. The course begins _____ 7 January and ends sometime _____ April
14. It was quite a short book and easy to read. I read it _____ a day
15. The telephone and the door bell rang _____ the same time
16. I might not be at home _____ Tuesday morning but I'll probably be there _____ the afternoon
17. Mary and Henry always go out for a meal _____ their wedding anniversary
18. Henry is 63. He'll be retiring from his job _____ two years' time
19. My car is being repaired at the garage. It will be ready _____ two hours
20. We usually have a holiday _____ the summer