1. Lewis Dot Structures of Covalent Compounds Atoms are made up of protons, neutrons, and electrons. The protons and neutrons are located at the center of the atom, the nucleus. These electrons can be divided into core electrons and valence electrons. The valence electrons are the outermost electrons and are the ones involved in chemical reactions

2. p+p+ e-e- p+p+ p+p+ e-e- e-e- n0n0 n0n0 n0n0 p+p+ p+p+ p+p+ p+p+ n0n0 n0n0 e-e- e-e- e-e- e-e- e-e- e-e- e-e- The Nucleus Protons and neutrons are located in the nucleus (center) of the atom Electrons Electrons occupy most of the volume of an atom They arrange themselves in ’shells’ at varying distances from the nucleus Valence electrons These are the outermost electrons and the ones In chemical reactions

3. The number of valence electrons varies by element. For the Main Group elements, the number of valence electrons is equal to the Group Number that the elements belong to. For example, Sodium (Na) belongs to Group 1A and therefore has 1 valence electron.

4. The Periodic Table

5. For example, Bromine (Br) belongs to Group VIIA and therefore has 7 valence electrons. We can represent the valence electrons of an atom using a Lewis dot symbol, in which the element symbol is surrounded by dots representing the valence electrons. For example, Oxygen has six valence electrons, so its Lewis dot symbol is: Note the six dots representing the six valence electrons

6. For example, neon has eight valence electrons, so its Lewis dot symbol is: For example, carbon has four valence electrons, so its Lewis dot symbol is :

7. How many valence electrons does Potassium (K) have? 1 How many valence electrons does Antimony (Sb) have? 5 How many valence electrons does Phosphorus (P) have? 5 How many valence electrons does Magnesium (Mg) have? 2

8. The Noble Gas elements in Group VIIIA have either two valence electrons (He) or eight valence electrons (Ne, Ar, Kr, Xe, and Rn). extremely stable because they have full valence shells-

9. Metallic elements at the left side of the Periodic Table tend to lose one or more electrons to form positive ions, such as Na + and Mg 2+, each of which has the electron configurationof the Noble Gas that preceds it. Nonmetals at the right side of the Periodic Table tend to either gain electrons to form negative ions such as F -, O 2-, and N 3- or to share electrons in covalent bonds.