BMAT Chemistry Q&A Study Guide

nucleus middle of the atom, contains protons and neutrons, positive charge protons positively charges neutrons no charge electrons negative charge number of protons equals number of electrons atoms of an element have the same number of protons one proton in nucleus hydrogen two protons in nucleus helium horizontal rows periods vertical colups groups elements in the same groupo similar properties group same number of electrons in their outer shell group 18 noble gases - eight electrons in the shell top nimer mass number - number of protons and neutrons bottom number atomic number - number of protons/electrons shell order 2,8,8 making bonds involves atoms giving away, taking or sharing electrons metal atoms lose electrons to form positive ions non metal atoms gain electrons to form negative ions