một nguyên tử có 19 êlectron . số lelectron ở lớp ngoài cùng của nguyên tử này là

Write the second sentence so that has a similar meaning to the first, beginning with the given words in the brackets. 1) When I was a child, we lived in London. (We used to...) 2) She is sorry she can't play the piano. (She wishes...) 3) I speak English badly, I can't speak to Linda. (If..) 4) I've studied English for two years. (I began...)

chọn từ và chia động từ , mình đang vội ạ

Câu 2: một chiếc đồng hồ đánh chuông theo giờ. Đúng 8 giờ, nó đánh 8 tiếng "boong", đúng 9 giờ, nó đánh 9 tiếng "boong", ..... Từ lúc đúng 8 giờ đến lúc 12 giờ trưa cùng ngày, nó đánh bao nhiêu tiếng " boong"

Giúp mk với mọi người ơi Mình đg cần gấp

Mọi người giúp em bài này nhe, Mong MOD đừng xóa, em cần gấp lấm

giúp câu 37 , 38,39,40,41,42,43,44,45,46,47,48

1. Rob's _______ as sales manager is now export manager of our main competitors. A predecessor B pioneer C precedent D ancestor 2. By this time next year, he __________ school, so he will want to take the dog for walks with me, or by himself. A will have started B started C will not start D will not have started 3. When you see my new bike, you ____________ love it! A will B can C would D must 4. Shoppers were encouraged to stay in the building for as long as possible____________ marvelous restaurants, a library and a Silence Room. A enjoying B have enjoyed C enjoy D will enjoy 5. Tom Sawyer was able to make ______ by pretending that the work was a specific privilege. A) his friends painting the fence B) his friends to paint the fence C) his friends paint the fence D) the fence paint his friends

Bài 2: Dựa vào quy tắc hóa trị, xác định hóa trị của a) Fe trong hợp chất Fe2O3.

Tìm x: a)1+2+3+...+x=19900 b)1+3+5+...+x=51 mũ 2