Это не элемент, а условное обозначение молекулы галогена - фтора, хлора. брома или иода
2Mg + O2 = 2MgO
n(MgO) 400/40=10
n(Mg)= (10*2)/2=10
m=10*24=240г
Dear,Max
Greetings from England.We're having great time here.The museums is very interesting.We are lucky with the weather.The sunshine everyday,but it's not very hot.Yesterday we had a cool day!We saw Big Ben!It's very long!
It's very beautiful here!We was in forest,we was in cafe.In cafe I ate pasta!
Write to me soon.
Take care,
Alex
3 s²p¹ это аллюминий. Al.