A high pressure system is a whirling mass of cool, dry air that generally brings fair weather and light winds. High pressure weather tend to be free of clouds. Without clouds, there is no rain and hence the weather tends to be clear and fair.
Once ignited, a ribbon of magnesium metal burns freely in air to form solid magnesium oxide in the form of a white powder. The reaction is plainly spontaneous even though ΔS is negative.
The atomic radius of main group elements generally increases down a group because as there are more electrons they are farther away from the nucleus and the electrons closer to the nucleus shield the outer electrons from the protons for attraction.
