CHEMISTRY

1. CHEMISTRY

2. Atoms, Elements & the Periodic Table Describe the structure & parts of an atom. Identify the properties of an atom. Interpret information on a periodic table to understand how elements are grouped.

3. What do you remember from 7th grade? • The periodic table shows approximately 120 known elements • Elements can be classified as metals, nonmetals, and metalloids • When two or more elements combine, they form a compound

4. What are the elements made of? • Element-the simplest pure substance. • Elements are made of atoms, and each element’s atoms are unique to that element • Atoms-the basic building blocks of all matter. They are the smallest particles into which an element can be divided and still be the same substance. • Atoms are made of 3 types of particles-protons, neutrons and electrons

5. The History of Atomic Theory

6. Democritus – 440 BCE • Greek Philosopher 2445 years ago. • Called particles that made up “stuff” ATOMS • Atomos (Greek word) • “not able to be divided”(uncuttable) • small hard particles • Constantly move

7. Dalton - 1803 • Atoms make up all substances (the elements) • Atoms can not be created, divided or destroyed. • Atoms combine to make other substances. • Conducted experiments

9. Dimitri Mendeleev • Proposed the laws of the periodic table • 1869-developed the first periodic table • Table was arranged according to increasing atomic weight • Left spaces for elements yet to be discovered

10. J.J. Thomson - 1897 • Discovered negatively charged particles in atoms called Electrons. • Conducted Cathode Ray Tube experiment • Led to the Plum Pudding Model

12. Ernest Rutherford - 1909 • Discovered the nucleus • Nucleus • Small tiny very dense center of atoms • Where most the atoms mass is located • Atoms are mostly empty space where electrons are found • Conducted the Gold Foil experiment

14. Niels Bohr - 1913 • Electrons move around the nucleus of atoms in definite paths. • Electrons jump between levels from path to path. • Bohr’s model

16. Most Recent Atomic Theory • Schrodinger and Heisenberg • Electron paths cannot be predicted. • Electrons are likely to be found in regions around the nucleus called electron clouds. • Called the electron cloud model.

17. Recent Discoveries • Chadwick • 1932-Discovered that neutrons exist in the nucleus of atoms • Neutrons have no charge and the mass equal to protons and help to stabilize the atom • Gell-Mann • 1969-Subatomic particles are made of smaller particles called quarks

19. PERIODIC TABLE =ORGANIZED ELEMENTS • Elements are: • PURE-Made of like atoms of that element • Identified by it’s atomic number (# of protons) • Arrangement of electrons determines the elements properties (such as conductivity and reactivity).

20. The Element Song Link to video http://www.privatehand.com/flash/elements7.swf Select broadband player.

21. The Structure of an Atom • Protons – POSITIVE charged particles inside the nucleus (center). • Neutrons – neutral particles inside the nucleus that have NO CHARGE! • Electrons – NEGATIVE CHARGED particles in atoms found around the nucleus.

22. Atomic Particles

23. Outside the nucleus • Can be called a electron cloud, shell, energy level, orbit or ring • Area outside the nucleus where electrons are found • 1st cloud=2 electrons • 2nd cloud=8 electrons • 3rd cloud=18 electrons

24. Boron (B) Atomic #=5 Atomic Mass=11 Protons=5 Neutrons=6 Electrons=5

25. Sodium-(Na) Atomic #=11 Atomic Mass=23 Protons=11 Neutrons=12 Electrons=11

27. Energy Levels - Electron Clouds • Regions around the nucleus where electrons are arranged. • Electrons further away from the nucleus have more and more energy. • Each level or cloud can hold a specific # of electrons. • 1st level - 2 electrons • 2nd level - up to 8 electrons • 3rd level-up to 18 electrons

28. Valence Electrons • The electrons in the outermost energy level (electron cloud). • Very important because they determine how an element will react with other substances

29. What’s in the Box?

30. Atomic Number 5 B 10.81 Boron • Equals the number of protons inside the nucleus of the atom. • Atomic Number=Number of Protons=the number of electrons • Determines the element. • All atoms of an element have the same atomic number. • No two elements have the same atomic number.

31. Symbol 5 B 10.81 Boron • All elements have their own unique symbol • Symbols can be one or two letters • The first letter is always a capital letter • The second is always a lower case letter • Symbols don’t always match their English word bc most are from Latin or Greek roots. • Example: Fe=Iron (English) Ferrum (Latin)

32. Mass Number 5 B 10.81 Boron • The total number of protons and neutrons in an atoms nucleus. • Number under the element symbol • Protons + Neutrons = Mass Number Practice: If an atom has 12 protons, 14 neutrons and 12 electrons, what is its mass number? Practice online

33. Atomic Mass Unit - amu • Unit of measurement for the mass of subatomic particles. • 1 amu = 1.7 X 10 -24 They are TEENY TINY!!! • .000000000000000000000017 grams • Proton = 1 amu • Neutrons = 1 amu • Electrons = almost zero (TINIEST particle with the least mass) • Most of the mass is in the nucleus with protons and neutrons • Otherwise atoms are mostly EMPTY SPACE

34. Atomic Mass • Refers to the weight of the atom. • Atomic Mass= Protons + Neutrons • Never negative Mass

35. The Charge of an atom • To find the charge of an atom- • Find the number of protons (+) • Find the number of electrons (-) • Represent the electrons as a negative number • Add the protons and electrons to find the charge • Ex: Calcium atom has 12 protons and 10 electrons. What is the charge of this atom? Answer 12 proton + 10 electrons 12 + (-10)= +2 This atom would be positive (+)

36. More practice with charge What is the charge of a copper atom with 26 electrons? What is the charge of a Sulfur atom with 18 electrons? 16 protons (+) + 18 electrons (-) 16-18=-2 negative 29 protons (+) + 26 electrons (-) 29-26=+3 positive

37. Review

38. Periodic Table Overview

39. How the Elements are Arranged Groups/Families: Similar properties Periods/Rows: Increasing atomic number/mass

40. Groups/Families • Columns of the periodic table that consist of elements that have the same number of valence electrons. • Groups 1 and 2 - same # as group • Groups 13-18 - 10 - the group # • Groups 3-12 - no general rule.

41. Periods • Rows of the periodic table that consist of elements with the same number of electron clouds or energy levels.

42. Alkali Metals • Group #1 • All metals • 1 Valence Electron • Very reactive

43. Alkaline-Earth Metals • Group #2 • All Metals • 2 Valence Electrons • Very reactive but less than group #1.

44. Transition Metals • Groups # 3-12 • All metals • 1-2 valence electrons • Less reactive than group #2 • Also contain lanthanide and actinide series (radioactive/unstable).

45. Groups # 13-16 • Elements change from metals to nonmetals and include the metalloids. • Atoms have 10 fewer valence electrons than the group #. • Boron Group #13 - 3 valence electrons • Carbon Group #14 - 4 valence electrons • Nitrogen Group #15 - 5 valence electrons • Oxygen Group #16 - 6 valence electrons

46. Halogens • Group 17 • All nonmetals • 7 valence electrons • Very reactive • Only need to gain 1 more electron.

47. Noble Gases • Group # 18 • All nonmetals • 8 valence electrons - except helium only has 2. • Unreactive • Have a full outer electron cloud (energy level).

48. Hydrogen stands alone 1 valence electron Very reactive Reacts violently with Oxygen under the right conditions.

49. Everyday Uses

50. Isotopes • Atoms of elements that have the same number of protons (atomic number) but a different number of neutrons inside the nucleus.