Một hạt nhân phóng xạ có thể phát ra hạt positron tức e+. Điều này tương ứng với một proton trong hạt nhân biến thành một neutron. Tuy nhiên khối lượng của neutron lại lớn hơn khối lượng của proton. Vậy làm thế nào để sự phát positron nói trên có thể xảy ra được?

Acylinder is filled with 2.00 moles of nitrogen, 3.00 moles of argon and 5.00 moles of helium. if the gas mixture is at stp, what is the partial pressure of the argon

Which type of bonding involves the complete transfer of a valence electron from a less electrogrative atom to a more electronegative one

The scheme below is from a series of reactions that are part of a synthesis of vitamin a. answer the following questions with reference to this scheme. (i) what is "reagent a"? (ii) draw a step-by-step mechanism which explains the formation of compound c from compound b (iii) which reagents would you use to form compound e from compounds c and d (reagents b and c)? for each reagent suggested above in (ii) explain the role of the reagent in the reaction to (iv) form compound e. you may wish to do this by drawing a mechanism. 1. addition of reagent a но reagent a 2. н,о" thо oh нон-с compound a. compound b. compound c .ch-оh 1. reagent b "сно 2. reagent c сh oh compound e. compound d.