Reactions and compounds. New substances are formed by chemical reactions. When elements react together to form compounds their atoms join to other atoms using chemical bonds. For example, iron and sulfur react together to form a compound called iron sulfide.Mixture of iron (grey) and sulfur (yellow) powders.hen elements react, their atoms join with other atoms to form compounds [compound: A compound is a substance formed by the chemical union (involving bond formation) of two or more elements. ] . Chemical bonds form when this happens, which involves atoms transferring or sharing electrons.
The 'red land' was the barren desert that protected Egypt on two sides. These deserts separated ancient Egypt from neighbouring countries and invading armies. They also provided the ancient Egyptians with a source for precious metals and semi-precious stones.
The Neolithic revolution has taken different paths in the neighbouring countries of Egypt and Sudan. This article examines these variations by comparing food production, settlement patterns, society and culture in Egypt and Sudan and analyses the reasons for the different developments.