1. Atomic Bonding & Water But first… DO NOW: 1 st : Take out homework so I can check it. Next: Write whether each of the following is an element, compound, atom or molecule: 1.The smallest piece of water (H 2 O) possible. 2.The smallest piece of carbon (C) possible. 3.A pile of sand (silicon dioxide SiO 2 ) 4.An old copper (Cu) penny.

2. Compounds An atomic bond is a force which joins atoms together to form a molecule Atomic bond Water O H H

3. Ionic Bonds: STRONG An atom loses 1 or more valence electrons, giving it a positive charge. Another atom gains the electron(s) and becomes negatively charged + & - ions attract. Na Cl e- - +

4. How Atomic Bonds Work Electrons are responsible for atomic bonding. There are 3 ways electrons can interact to form bonds

5. Covalent bonds: STRONG 2 atoms share a pair of valence electrons H e- H

6. Polar Bonds: STRONG In a polar bond, electrons are shared unevenly. Since electrons are negative, the atom that attracts electrons the most becomes a little negative, and the atom losing the electrons becomes a little positive.

7. Water is Polar Molecules with positive and negative parts are called polar molecules. Polar molecules form hydrogen bonds

8. Hydrogen Bond: Pathetically WEAK! A Hydrogen bond is a weak bond between 2 different polar molecules

10. What Were Those Properties?

11. High Surface Tension Water’s high surface tension causes: Cohesion: Water sticking to Water Adhesion: Water sticking to other surfaces

12. High Melting & Boiling Points

13. Density Anomaly Ice floats on water! Water is one of the only compounds known that gets less dense when it freezes!

14. Solvent Properties Water is very good at dissolving substances.

15. But WHY??? Water has all of those weird properties happen because of 1 simple thing… POLARITY

16. Water is a polar molecule It has a positive and negative side, causing hydrogen bonds

17. HOMEWORK Read Section 3-1, pp. 49-51 Answer #1-5 p. 51