COS 1.0, 1.1, 1.2, 1.3

1. COS 1.0, 1.1, 1.2, 1.3 • RECOGNIZE PERIODIC TRENDS OF ELEMENTS, INLCUDING THE NUMBER OF VALENCE ELECTRONS, ATOMIC SIZE AND REACTIVITY. • CATEGORIZE ELEMENTS AS METALS, NONMETALS, METALLOIDS AND NOBLE GASES. • DIFFERENTIATE BETWEEN FAMILIES AND PERIODS. • USE ATOMIC NUMBER AND MASS NUMBER AND MASS NUMBER TO IDENTIFY ISOTOPES.

2. WHAT YOU’LL LEARN • State the charge, mass, & location of each part of an atom according to the modern model of the atom. • Relate the organization of the periodic table to the arrangement of electrons within an atom. • Identify isotopes of common elements. • Determine how many protons, neutrons, & electrons an atom has, given its symbol, atomic number, & mass number. • Locate alkali metals, alkaline earth metals, & transition metals in the periodic table. • Locate semiconductors, halogens, & noble gases in the periodic table.

3. ATOMIC STRUCTURE

4. WHAT ARE ATOMS? • smallest part of an element that still has element’s properties. • building blocks of molecules

5. WHAT’S IN AN ATOM?

6. NUCLEUS • center of each atom • small & dense • has positive electric charge

7. PROTONS • subatomic particle that has positive charge • found in nucleus

8. NEUTRONS • subatomic particle that has no charge • no overall charge • equal number of protons and electrons whose charges exactly cancel

9. ELECTRONS • subatomic particles with negative charges. • located in a cloud (orbit) moving around outside nucleus

10. QUARKS • particles of matter that make up protons and neutrons

11. MODELS OF THE ATOM

12. DEMOCRITUS • Greek philosopher • developed theory around 400 B.C. • proposed that atoms make up all substances • Atom — “unable to be divided”

13. JOHN DALTON • Developed atomic theory in 1808 • first atomic theory with a scientific basis • model was simple sphere • thought the atom could not be split • Atoms of same element exactly alike

14. J.J. Thomson (1897) • Discovered negatively charged particles • atom was divisible! • Particles discovered are electrons • Atom consists of positively charged material with negative charges spread evenly throughout

15. Rutherford (1908) • Gold Foil Experiment • Positive particles shot at gold foil occasionally bounced back! • Proposed dense, positively charged center called the nucleus

16. NIELS BOHR • theory developed in 1913 • suggested that electrons in an atom move in set paths around the nucleus much like planets orbit sun It is impossible to determine an electrons: • exact location • speed • direction Best scientists can do is: • calculate chance of finding an electron in a certain place within an atom

17. ENERGY LEVELS • path of a given electron's orbit around a nucleus, marked by a constant distance from the nucleus • Closer to nucleus, lower energy level of electrons • Further from nucleus, more energy electrons have • Number of filled energy levels an atom has depends on number of electrons

18. ORBITAL • region in an atom where there is a high probability of finding electrons

19. VALENCE ELECTRONS • found in outermost shell of an atom • determines atom’s chemical properties • participate in chemical bonding • Every atom has between one and eight

20. THE PERIODIC TABLE

21. ORGANIZATION OF THE PERIODIC TABLE • Groups similar elements together • organization makes it easier to predict properties of an element based on where it is in periodic table • Elements are listed in order of number of protons

22. PERIODIC LAW • states that when elements are arranged this way, similarities in their properties will occur in a regular pattern • helps determine electron arrangement

23. PERIODS • Horizontal rows • number of protons & electrons increases as you move from left to right

24. FAMILY/GROUP • vertical column of elements • Atoms of elements in same group have same number of valence electrons • elements have similar properties

25. IONS • an atom or group of atoms that has lost or gained one electron and has a negative or positive charge

26. HOW THE STRUCTURES OF ATOMS DIFFER

27. ATOMIC NUMBER (Z) • number of protons in the nucleus

28. MASS NUMBER (A) • number of protons plus the number of neutrons in nucleus

29. ATOMIC RADIUS • is size of atom GROUPS • radius increases as one proceeds down any group of periodic table WHY? • adding layers of electrons PERIODS • radius decreases as one proceeds across any row of periodic table WHY? • increasing number of protons in nucleus as you go across the period pulls electrons in more tightly.

30. ISOTOPE • has same number of protons as other atoms of same element do but has a different number of neutrons. • Some are more common than others. • If you know the atomic number and mass number of an atom, you can calculate the number of neutrons it has.

31. Example Chlorine 35 has a mass number of 35. Has an atomic number of 17. • Mass number (A): 35 • Atomic number (Z): –17 • Number of neutrons: 18

32. ATOMIC MASS UNIT (amu) • Mass of an atom or molecule that is exactly 1/12th the mass of a carbon atom with mass number 12

33. AVERAGE ATOMIC MASS • weighted average of masses of all naturally-occurring isotopes of an element

34. Avg. Atomic Mass AVERAGE ATOMIC MASS EXAMPLE • About 8 out of 10 chlorine atoms are chlorine-35. Two out of 10 are chlorine-37. 35.4 u

35. FAMILIES OF ELEMENTS

36. HOW ARE ELEMENTS CLASSIFIED? • By similar physical & chemical properties.

37. ALKALI METALS • group 1 • shiny • malleable • ductile • React violently w/ water • Very reactive b/c it has only one valence electron • Has +1 charge • Not found in nature as elements • Found only in compounds • Ex: salt (NaCl) Lithium • used to treat bipolar disorder

38. ALKALI EARTH METALS • Group 2 • two valence electrons • +2 charge • shiny • malleable • ductile • Form compounds in stone & human body Calcium (Ca): • Shells of sea animals, coral reefs (limestone), skeletal structure humans … Magnesium (Mg) • Air plane construction • Activates enzymes that speed up processes in humans • brilliant white color in fireworks Medicines • milk of magnesia • Epsom salt

39. TRANSITION METALS • groups 3-12 • most familiar • found in elemental state Iron • most abundant metal • used in steel Aluminum • making containers, automotive parts, cookware… MERCURY • only metal at room temperature • used in thermostats, thermometers, batteries …

40. NONMETALS • Some elements found in groups 13-16 & all elements in groups 17-18 • except hydrogen • usually gases or brittle solids at room temperature • poor conductor of heat & electricity • may be solids, liquids, or gases at room temperature.

41. HALOGENS • Group 17 • very reactive in elemental state Chlorine • greenish yellow gas • Kills bacteria • Elemental chlorine is very poisonous • obtained from seawater Fluorine • Poisonous yellow gas • used in toothpaste Bromine • Dark red liquid • only nonmetal liquid at room temperature • obtained from seawater Iodine • shiny, purple-gray solid • Used as disinfectant • obtained from seawater

42. NOBLE GASES • group 18 • Exist only as single atoms instead of molecules • Unreactive b/c orbitals are full of electrons Neon • Signs Helium • Less dense than air • Gives lift to blimps & balloons Argon/Krypton • Used in light bulbs

43. SEMICONDUCTORS • elements that can conduct electricity under certain conditions • Aka metalloids: • Composed of only six elements • Boron, silicon, germanium, arsenic, antimony & tellurium Boron • Extremely hard • Added to steel to increase hardness & strength at high temperatures. Antimony • Used as fire retardants Silicon • Makes up 28% of earths crust • Sand most common compound • Used in electronics