The Atom and the Periodic Table

1. The Atom and the Periodic Table

2. Atoms http://library.thinkquest.org/12659/media/solar_system/sun/sun.jpg • Everything in the Universe is made of stuff (also known as matter). • The building blocks are the same, whether we are looking at Stars or Starbursts. http://www.jakehowlett.com/tuckshop/wrappers/sweets/fruits/starburst.jpg

3. Atoms • Matter is made up of Atoms. • Atoms are the smallest particle of an element. • They are so small that: • 1 sheet of paper = 10,000 atoms thick • 1 drop of water has 2 trillion atoms of oxygen and 4 trillion atoms of hydrogen. • The three parts of an atom are: • Protons • Neutrons • Electrons

4. Atoms – Protons • There are three types of particles that make up atoms • The first type of particle is called the PROTON. • Protons are found in the nucleus of an atom. • Protons have a positive (+) charge. • Protons have a mass of 1 a.m.u.

5. Atoms - Neutrons • Another particle is the NEUTRON. • Neutrons are also found in the nucleus of an atom. • Neutrons have no charge. We call this neutral. • Neutrons have a mass of 1 a.m.u. • Neutrons act like the glue that holds the nucleus together.

6. Atoms - Electrons • Electrons are the third type of particle inside of an atom. • They are very small, and exist outside of the nucleus in the electrons clouds or shells. • Electrons have a negative charge (-) and have almost no mass at all.

7. Subatomic = smaller than an atom Atomic Structure • Atoms are made up of three subatomic particles: In nucleus 1 a.m.u + In nucleus none 1 a.m.u Outside nucleus - No, negligible

8. Atomic Structure Video

9. Elements • Substances made of only one type of atom • Identified by atomic number (protons!!!) • Can not be broken down into simpler substances

10. Element Symbols • Shorthand name of the element • Most are based on the Latin name • Ex: Gold = Au • The symbol is either: • One capital letter -ex: Carbon = C • Two letters…one capitol, one lower case -ex: Krypton = Kr

11. Atomic Number 1 H • Top Number indicates Atomic Number • Atomic Number = Number of Protons • Hydrogen: • Atomic Number 1 = 1 proton • Magnesium: • Atomic Number 12 = 12 protons • Lead: • Atomic Number 82 = 82 Protons • IF YOU CHANGE THE NUMBER OF PROTONS OF AN ATOM, YOU CHANGE ITS IDENTITY!!!!!!!! 12 Mg 82 Pb

12. Atomic Mass H 1 • Bottom Number indicates Atomic Mass • Atomic Mass = Total Mass (Number of Protons + Number of Neutrons) • Hydrogen: • 1 (Protons + Neutrons) • Magnesium: • 24 (Protons + Neutrons) • Lead: • 207 (Protons + Neutrons) • If we take the Atomic Mass and subtract the Atomic Number, we can figure out the number of neutrons. • Pb – • (Atomic Mass) • 207 • – • (Atomic Number) • 82 • = • 125 Mg 24 Pb 207

13. Atomic Structure (cont.) • Atomic Mass • Average mass of an element, based on amount of each isotope found in nature • Not a whole number because it is an average • Atomic number • Number of protons in an element • Also, number of electrons when it is neutral (has no charge)

14. Atomic Structure (cont.) • For a lithium (Li) atom: • What is the atomic number? 3 3 • How many protons? • How many electrons since it is neutral? • What is the atomic mass? 3 6.939 rounded to 7 • How many neutrons? Usually 4

15. Atomic Structure (cont.) • Practice Problem #1 • For a sodium atom: • What is the atomic number? • How many protons? • How many electrons since it is neutral? • What is the atomic weight? • How many neutrons? 11 11 11 22.99 rounded to 23 Usually 12

16. Atomic Structure (cont.) • Practice Problem #2 • For a boron atom: • What is the atomic number? • How many protons? • How many electrons since it is neutral? • What is the atomic weight? • How many neutrons? 5 5 5 10.811 rounded to 11 Often 6

17. Periods • The elements are arranged on the periodic table of elements • Going horizontal across the table are the PERIODS • Starting from the left, the periods go from metals  metalloids  nonmetals

18. The Periodic Table • Organized by trends and patterns • “periodic” means repeating • This allows you to make predictions about the atoms’ behavior based on where they are on the table

20. Metals • Lose electrons to form positive ions • Ductile & Malleable • What do these words mean? • Good conductors of heat and electricity • MOST are solid at room temperature

21. Nonmetals • Gain electrons to form negative ions • Brittle • Good insulators • Found as solid, liquid, or gas at room temp

22. Metalloids (semi-metals) • Found directly on either side of side-step line • Except Al (this is a metal!!!) • Properties of both metals and nonmetals • Less conductive than metals, but poorer insulators than nonmetals • Electrons held more tightly than metals, but can be freed with heat

23. Periodic Table - History Dimitry Mendeleev was a Russian (actually Siberian) scientist that lived in the late 19th Century.

24. Periodic Table - History • When Mendeleev arranged them by Atomic Mass, he was able to predict the properties of elements that had not yet been discovered. • This is the basis of the Periodic Table that we use today.

25. Periodic Table - History Now the Periodic Table that we use is arranged by Atomic Number instead of Mass. Henry Moseley reordered the Periodic Table by Atomic Number

26. Groups and Families • The columns on the periodic table are called groups and families. • The groups are the numbers; the families are the names • They are organized by the number of valence electrons

27. Alkali Metals • Group 1A • Only one valence electron • VERY reactive!!!! • Hydrogen is NOT included

28. Alkaline Earth Metals • Group 2A • Two valence electrons • Not as reactive as the alkali metals • Named because of where they are found on Earth

29. Transition Metals • Found in the middle of the table • In the “B Groups” • Can change their number of valence electrons Bottom Rows are also known as the Rare Earth Metals!!!

30. Halogens • Group 7A • Seven valence electrons • VERY reactive!!!!

31. Noble Gases • Group 8A • 8 valence electrons—outer energy level is full • Very UNREACTIVE—what do they need to be 

32. Electron Clouds • The different layers of clouds hold different numbers of electrons • 1st cloud = 2 • 2nd cloud = 8 • 3rd cloud = 8 These cloud layers conveniently match the rows on the periodic table: 1st row = 2 elements 2nd row = 8 elements 3rd row =8 elements… And then it gets complicated

33. Electron Clouds (cont.) • To draw the electron clouds: • Figure out how many total electrons • Fill in the electrons starting with the first cloud • Sulfur has: • 16 electrons

34. This is WAY too much work…there must be a simpler way! Electron Clouds (cont.) • Practice Problem • Draw the electron clouds for an Al atom

35. Lewis Dot Structures • A smart man named Gilbert Newton Lewis figured out an easier way! • For Lewis Dot Structures draw only theimportant electrons…are called the outer, or valence, electrons Just draw the outer electrons around the atomic symbol S

36. Ca Cl O Lewis Dot Structures (cont.) • Practice Problem #4 • Draw Lewis Dot Structures for: • A Calcium atom • A Chlorine atom • An Oxygen atom

37. Octet Rule • Noble gases are what all elements aspire to be like electronically • These elements have 8 electrons in highest energy level • 8 is GREAT

38. Lewis Dot Structures (cont.) • All elements want to be full of electrons: • So they gain or lose electrons until they are full • This gives the atom a charge • Negative charge if they gain electrons • Positive charge if they lose electrons Charged atoms are called ions: cations if they are positive and anions if they are negative

39. Atomic Number Continued +1 K • Also equal to number of electrons if the atom has no charge • If the Element has a positive charge • Take the atomic number and Subtract the charge to find # of electrons • K • (Atomic Number) • 19 • - • (Charge) • 1 • = • 18 Electrons • Ca • ? • If the element has a negative charge • Take the atomic number and Add the charge to find the number of electrons • Cl • 17 • + • 1 • = • 18 Electrons +2 Ca -1 Cl

40. Ions • How many valence electrons in Li? • Is it easier to gain or lose to become full? • How many will it gain or lose? • What charge will it become? 1 lose 1 +1

41. Ions • How many valence electrons in O? • Is it easier to gain or lose to become full? • How many will it gain or lose? • What charge will it become? 6 gain 2 -2

42. Ions

43. Atomic Tables • Rules • Name • Comes from Periodic Table WITH Mass Number • Symbol • Comes from Periodic Table • Atomic Number • Top Number, Same as number of Protons • Mass Number • Equal to Number of Protons + Number of Neutrons • (Usually Bottom Number of Periodic Table Rounded)

44. Atomic Tables Continued • Protons • Equal to Atomic Number (Top) • Neutrons • = Mass Number – Number of Protons • Electrons • If No Charge • Equal to Number of Protons • If Has a Positive Charge • Subtract Charge from Number of Protons • If Has a Negative Charge • Add Charge to Number of Protons

45. Practice Problems Neon-20 Ne 10 10 10 20 Iron-56 Fe 26 56 26 Sodium-23 11 11 12 10 Sulfur-32 S 32 16 18 15 8 -3 N 7 7