How do you number the groups of a periodic table?

What diagram shows the ionic compound of magnesium oxide

Each pair of clay balls represents to planetesimals if each plane test molluscum pound of the same material and is separated by the same distance which pair experiences the greatest gravitational attraction

Scientific evidence tells us that the cause of earths four season is the tilt of earth as it revolves around the sun. the student is instructed to illustrate this information in a science notebook. how will the student illiterate winter in the northern hemisphere?