2. Valence Electrons Outer most shell of electrons Held loosely to an atom Key to all chemistry All atoms want to have full shells 12
3. Electron Dot Diagrams H C O Use the symbol for each element with a dot for each outer electron. Identify each element and the number of valence electrons that it has. Hydrogen 1 Carbon 4 Oxygen 6 13
5. Bonding I (At #53) has how many valence electrons? What will it do to fill its shells? Mg (At #12) has how many valence electrons? What will it do to fill its shells? Atoms always to the easiest thing! Mg will always lose 2 electrons never gain 6 7 Gain 1 electron 2 Gain 6 or lose 2 electrons 13
6. Bonding Where do extra electrons go? Where can atoms find the electrons they need? Atoms trade electrons = Chemical bond *The fewer electrons you need to trade the more reactive the atom will be! When atoms bond, new substances are made. 13
7. Review How are element represented in the periodic table? By symbol The ____________ of an element is the number of protons in the nucleus of the atom What is a row of elements across the table called? Period Describe how the atomic number changes across a period of elements. Each element increases by 1 atomic number atomic number 14
8. Review What are the elements in the same column called? Group or family Elements within a group always have the same number of Valence Electrons 16
9. Nonmetals How many valence electrons do non-metals have 4 or more Describe two ways that non-metals can combine with other elements. Combine with metals to gain electrons Combine with other non-metals to share electrons 19