4、地球物质的化学组成 Rock and Minerals inearth Atomic Structure All natural and most synthetic substances on earth are made from the ninety naturally occurring chemical elements. An atom is the smallest particle into which an element can be divided while still retaining the chemical characteristics of that element (fig 3. 1). The nucleus, at the center of the atom, contains one or more particles with a positive electrical charge(protons Dif and usually some particles of similar mass that have no charge(neutrons Hf ) Circling the nucleus *k are the negatively charged electrons 环质 Environmental Geology环境地质学 Environmental Geology 4、地球物质的化学组成 Rock and Minerals in earth Atomic Structure All natural and most synthetic substances on earth are made from the ninety naturally occurring chemical elements. An atom is the smallest particle into which an element can be divided while still retaining the chemical characteristics of that element (fig 3.1). The nucleus, at the center of the atom, contains one or more particles with a positive electrical charge (protons质子) and usually some particles of similar mass that have no charge (neutrons中子 ). Circling the nucleus核 are the negatively charged electrons