1. A TOMS AND THE P ERIODIC T ABLE Date: 8/19/13 Pg. 23 in ILL

2. A TOMS Atoms are the building blocks of all matter. Atoms are comprised of a nucleus (at its center) and an electron cloud (surrounding the nucleus).

3. A TOMS S UBATOMIC P ARTICLES Atoms are comprised of 3 subatomic particles. Protons—positively charged; found in the nucleus; have a mass of 1 atomic mass unit (amu) Neutrons—no charge; found in the nucleus; have a mass of 1 amu Electrons—negatively charged; found in the electron cloud; much smaller than protons and neutrons

4. A TOMS E LECTRON C LOUD M ODEL The current theory used to define what an atom looks like is called the electron cloud theory. States that an atom has a nucleus that is surrounded by an electron cloud with energy levels (layers) that hold a certain number of electrons and the electrons fill the energy levels closest to the nucleus first.

5. A TOMS E LECTRON C LOUD M ODEL ( CONT.) Electrons orbit the nucleus somewhere in their energy level, so the model shows a general area where the electrons are found (not specific orbits like the planets around the sun).

6. A TOMS V ALENCE E LECTRONS Valence electrons are found in the outermost energy level of the electron cloud (called the valence shell) and are the only ones involved in bonding. Determine: the chemical properties of an element reactivity—the ability of an atom to undergo a chemical reaction with another atom

7. A TOMS V ALENCE E LECTRONS ( CONT.) 8 is the “magic” number—if there are 8 valence electrons, the atom is stable and doesn’t want to react with other atoms Hydrogen, helium, lithium, and beryllium are the exceptions. They only need 2 valence electrons for stability.

8. A TOMS Valence Shell

9. P ERIODIC T ABLE E LEMENTS An element is a substance that cannot be broken down into simpler substances by ordinary chemical changes and consists of only one kind of atom.

10. P ERIODIC T ABLE D IMITRI M ENDELEEV On of the first scientist to notice the relationship between the elements based on their properties was Dimitri Mendeleev. Mendeleev created the periodic table of elements in 1869 with the 63 elements that were known to exist at the time. Mendeleev said that the properties of unknown elements could be predicted based on the properties of the elements around the missing one.

11. P ERIODIC T ABLE The periodic table is a chart containing all of the elements arranged by atomic number and atomic mass. Each element is given a symbol with 1 or 2 letters (the 1 st letter is always capitalized and, if present, the 2 nd is always lowercase) based on either the English or Latin name. The table is designed to show patterns in the properties of the elements.

12. P ERIODIC T ABLE atomic number The number of protons in one atom of an element. Also the number of electrons but ONLY IN NEUTRAL ATOMS. symbol Represents the element. atomic mass The mass of one atom of the element. Can be used to find the number of neutrons. atomic mass - atomic number = # of neutrons 8 O 16.00 Oxygen ROUND TO THE NEAREST WHOLE NUMBER

13. P ERIODIC T ABLE P ERIODS Each horizontal row of the periodic table is called a period. The atomic number, atomic mass, and the number of valence electrons all increase from left to right. The transition metals are an exception because the number of valence electrons varies.

14. P ERIODIC T ABLE G ROUPS /F AMILIES Each column of the periodic table is called a group or family. Each one is given a name to show the elements in the group share the same characteristics and behave the same way. Elements of the same group have the same number of valence electrons (except transition metals).

15. C OLOR C ODE Y OUR P ERIODIC T ABLE ! ( PGS D20-21 IN THE TEXTBOOK ) follow the teacher’s instructions for making a “cheat sheet” for determining valence electrons color code (you choose your own colors) your periodic table so that it shows the following: metals nonmetals metalloids create a color key for your periodic table

16. P UT YOUR TABLE TO WORK... How many valence electrons does phosphorus (P) have? What is the symbol for magnesium? What is the atomic mass of copper (Cu)? How many protons does silicon (Si) have? How many total electrons does carbon (C) have? How many neutrons are in iron (Fe)? Is calcium (Ca) a metal, nonmetal,or metalloid?