3. What is an Atom? Atom: Smallest unit of all matter 3 Main Parts: –1) Proton (+ charge) –2) Neutron (No charge) –3) Electron (- charge) Protons & Electrons usually equal in number Elements (substance made of only 1 type of atom) are identified on the Periodic Table

4. Reading the Periodic Table Atomic Number: Number of protons the atom contains –Usually # of electrons also Atomic Mass: Combined # of protons and neutrons inside the nucleus –Electrons too small to affect mass How many protons, electrons, and neutrons does Carbon contain? Protons = ______ Electrons = ______ Neutrons = ______

5. What’s the: A)Atomic number of Beryllium? B) Atomic mass of Beryllium? C) How many protons? D) How many electrons? E) How many neutrons? 4 9 4 4 5

6. Electrons orbit the nucleus in “energy levels” 1 st level: closest to nucleus stable w/ 2 electrons 2 nd level: stable w/ 8 electrons 3 rd level: stable w/ 8 electrons Atoms are stable when the outermost level is “full” Examine Carbon below. It has 2 electrons in the first level and 4 electrons in the 2 nd level. Is Carbon stable?

7. Molecule: 2 or more atoms held together by a covalent bond –Form when atoms are unstable Covalent Bond: Chemical bond where atoms share electrons –Ex: Oxygen atom Why unstable? Only 6 electrons in outer energy level What happens? Each oxygen atom will share two electrons with the other oxygen End result? Both will have 8 electrons in its outer level (O 2 is created)

8. Ionic bond: chemical bond where electrons are gained/lost Held together by magnetic attraction Cause: 1 atom may steal an electron from another Ion: + or – charged atom Ex: Sodium + Chlorine = Sodium Chloride e e ee e e ee e e e e e ee e e ee e e ee e e ee e

9. NaCl Protons (+) Electrons (-) Net charge 11+17+ 11-17- 00 Before bonding e e ee e e ee e e e e e ee e e ee e e ee e e ee e sodium chlorine After bonding NaCl Protons (+) Electrons (-) Net charge 11+ 17+ 10-18- +1

10. REview 1)Name the 3 subatomic particles. 2)Which subatomic particles are found inside the nucleus? 3)The atomic number usually allows us to determine the amount of which two subatomic particles? 4)If an atom has the atomic mass of 14 and the atomic number of 6, how many protons, neutrons, and electrons does the atom contain? 5)After an ionic bond is formed, what is the charge of the atom that gained an electron? 6)Which type of chemical bond shares electrons?