Bohr Model Bohr diagrams show how many electrons appear in each electron shell around an atom The first electron shell holds 2 electrons The second electron shell holds 8 electrons (Stable Octet) The third electron shell holds 8 electrons The fourth electron shell holds 18 electrons Example Beryllium 4 protons, 5 neutrons 4 electrons 4p 5n

BOHR MODELS Noble gases are very unreactive (stable) because the outer shell is full of electron Outer shell electrons are called valence electrons Other atoms gain or lose electrons in order to achieve the stability of noble gases. Gaining or losing electrons makes atoms into ions

Ion Formation RECAP Metals tend to lose electrons and written: Na+1, Be2+ Positive ions are called CATIONS Non-Metals tend to gain electrons O2-, F1- Negative ions are called ANIONS

Draw the Bohr Nitrogen Ion 3- 7p 7 n Nitrogen atom has atomic number of 7 and atomic mass of 14 - 7 protons, 7 neutrons, and 7 electrons Nitrogen ion has 3- ion charge gains 3 electrons So Nitrogen Ion has 7 protons, 7 neutrons, and 10 electrons

Draw the Bohr Beryllium Ion 2+ 4p 5n Beryllium atom has atomic number 4 and atomic mass of 9 - 4 protons, 5 neutrons, and 4 electrons Beryllium ion has 2+ ion charge loses 2 electrons So Beryllium Ion has 4 protons, 5 neutrons, and 2 electrons