*Elements, Atoms, and Ions. Title: Aug 30 6:07 PM (1 of 29)

Transcription

1 Chapter 3 Chemical Foundations *Elements, Atoms, and Ions Title: Aug 30 6:07 PM (1 of 29)

2 Section 3.1 and 3.2 The Elements Three uses of the term "Element" 1. Element: A sample of the element large enough to weigh on a balance 2. Element: 1 single atom of an element. 3. Element: A molecule of two or more of the same element bonded together. How do we represent Elements? *Element Symbols The first letter of the symbol is always capitalized. The second letter of the symbol is always in lower case. *What is the symbol for each of the following elements? Title: Sec 3.1 & 3.2 (2 of 29)

3 Section 3.3 Dalton's Atomic Theory What are the 5 statements summarized by John Dalton ( )? 1. Elements are made of tiny particles called atoms. 2. All atoms of a given element are identical 3. The atoms of a given element are different from those of any other element 4. Atoms of 1 element can combine with atoms of other elements to form compounds. A given compound always has the same relative numbers and types of atoms. 5. Atoms are indivisible in chemical processes. That is, atoms are not created or destroyed in chemical reactions. Compounds! Notice the number of atoms of each type in the molecule is represented by a subscript, except when it is 1. (NO, NO2, N2O) Title: Sec 3.3 (3 of 29)

4 Section 3.4 Formulas and Compounds *Compound 2 or more different elements bonded together *Chemical Formula shows the type and number of atoms bonded together in a compound Let's Practice! Write the formula for each of the following compounds, listing the elements in the order given. 1. A molecule containing six carbon atoms and six hydrogen atoms. 2. A compound containing one calcium atom and two chlorine atoms. 3. A compound containing one sodium atom, one nitrogen atom, and three oxygen atoms. Title: Sec 3.4 (4 of 29)

5 Section 3.5 Structure of the Atom (History) I. 2 Models of the Atom A. J.J. Thomson (1800's) Information gathered from cathode ray tube (CRT) experiments led to the discovery of the mass and charge of the electron first. (1) Electron Characteristics a very small particle with a negative charge (2) View of Model Plum Pudding * Plum Pudding Demo * Cathode Ray Tube Demo Figure 3.3 Plum Pudding Model Title: Sec 3.5 (5 of 29)

6 B. Rutherford's model Two regions of the atom the nucleus and empty space (1) Rutherford's gold foil experiment (1909) led to the discovery of the nucleus. (2) Nucleus the positively charged, dense central portion of the atom. Contains nearly all the atom's mass but takes up an insignificant fraction of its volume. Proton positively charged particle nearly 2000 X's (1836) larger than the mass of an electron, but equal to the negative charge of the electron. Mass = X 10 24grams Neutron electrically neutral nuclear particles equal in mass to the proton. discovered by Chadwick.(1932) mass = x 10 24grams. Title: Rutherford (6 of 29)

7 (3) The nucleus is held together by short range forces called nuclear forces neutron neutron forces, proton proton forces, and neutron proton forces. (a) Similar electrically charged particles generally repel one another; however, up to 100 protons can exist close together in a nucleus when up to about 150 neutrons are also present. (b) The relative size of atomic particles the overall size of the atom is 40,000 X's greater than the nucleus! Title: Sep 12 7:40 PM (7 of 29)

8 3.6 Modern Concept of Atomic Structure Particle Mass Actual Mass Relative Location Number (grams) charge Proton Electron Neutron Today's view of the Atom Tiny nucleus (about 10 13cm in diameter) Nucleus contains protons+ and neutrons0 Neutron functions to help to hold the protons (which repel each other) *Why do would protons repel each other? Electrons are found outside of the nucleus. They have the opposite charge of protons and are much smaller. *They are important determining chemical properties ***If all atoms are composed of these same components (electrons, protons, and nuetrons), why do differeent atoms have different chemical properties? Depends on number and arrangement of electrons! ANSWER Title: Sec 3.6 (8 of 29)

9 The an element is the number of in the nucleus of each atom of that element. The mass number or is the total number of protons and in the nucleus. Protons = Electrons = Neutrons = Title: Summary (9 of 29)

10 Title: Practice (10 of 29) PRACTICE!!!!

11 Section 3.7 Isotopes Isotope atoms with same number of prtons but different number of neutrons *Behave the same chemically because not changing the electron # or arrangement! Atomic Number # of protons in a nucleus Mass Number Sum of protons and nuetrons in an atom's nucleus Title: Sec 3.7 (11 of 29)

12 A X Z X = symbol of the element A = the mass number (sum of p + n) Z = the atomic number (number of p) Where is almost all the mass in an atom? If mass number is the sum of the protons and neutrons...how do you calculate the number of neutrons? (A Z) = # of Neutrons or (Mass # ANSWER Atomic number ) = # of Neutrons Title: Sep 13 2:04 PM (12 of 29)

13 Nuclear Protons Electrons Neutrons Hyphen Notation Notation Pd 42 S Cs Ba U 92 Cf 158 Kr Title: Sep 17 7:08 PM (13 of 29)

14 Isotopes are atoms of the same element with different masses. The number of protons in the nucleus determines the identity of an atom. For example, all hydrogen atoms contain only one proton. An atom that contains more than one proton in its nucleus is an atom of an element other than hydrogen. Hydrogen atoms, like those of all naturally occurring elements, contain varying numbers of neutrons. The most common type of hydrogen isotope has one proton only. It is sometimes called Protium. Protium makes up % of naturally occurring hydrogen. A deuterium atoms contains one proton and one neutron. The third form of hydrogen is known as tritium, which is radioactive. It contains one proton, and two neutrons. Title: Sep 14 9:57 PM (14 of 29)

15 Isotopes and Average Atomic Mass Elements come in a variety of isotopes, meaning they are made of atoms with the same atomic number but different atomic masses. These atoms differ in the number of neutrons. The average atomic mass is the weighted average of all the isotopes of an element EXAMPLE: A sample of cesium is 75% 133Cs, 20% 132Cs, and 5% 134Cs. What is its average atomic mass Title: Calc Average Atomic Mass (15 of 29)

16 Isotopes and Average Atomic Mass Elements come in a variety of isotopes, meaning they are made up of atoms with the sme atomic number but different atomic masses. These atoms differ in the number of neutrons. The average atomic mass is the weighted average of all the isotopes of an element. Determine the average atomic mass of the following mixtures of isotopes % 127I, 17% 126I, 3% 128I 2. 50% 197Au, 50% 198Au 3. 15% 55Fe, 85% 56Fe 4. 99% 1H, 0.8% 2H, 0.2% 3H 5. 95% 14N, 3% 15N, 2% 16N 6. 98% 12C, 2% 14C Title: Sep 17 8:10 PM (16 of 29)

17 Questions: 1. How many neutrons does Zn 66 (atomic number 30) have? 2. Ag 109 has 62 neutrons. How many electrons does the neutral atom have? 3. An atom of chlorine has an atomic number of 17 and a mass number of 35. How many protons, electrons and neutrons does it have? P E N 4. How many electrons does scandium (Sc) have? 5. How many protons does tungsten (W) have? 6. How many neutrons does Einsteinium 254 (Es 254) have? 7. How many average neutrons does platinum (Pt) have? 8. How many protons does arsenic 75 (As 75) have? 9. How many neutrons does krypton 85 (Kr 85) have? 10. How many electrons does titanium (Ti) have? 11. How many protons does radon (Rn) have? 12. Give the hyphen notation for this atom: p = 76 e = 76 n = Give the nuclear symbol notation for this atom: p = 11 e = 11 n = What is the relationship between an atom containing 4 protons, 4 electrons and 5 neutrons and one containing 5 protons, 5 electrons, and 4 neutrons? 15. What is the relationship between an atom containing 7 protons, 7 electrons and 8 neutrons and one containing 7 protons, 7 electrons, and 7 neutrons? 16. According to the Periodic Chart of the Elements, which element listed has an average of 58 neutrons? Title: Sep 17 8:11 PM (17 of 29)

18 Periodic Table Structure Mendeleev *Developed one of the first periodic tables and arranged it according to increasing atomic mass In the periodic table the horizontal rows are called and the vertical columns are called or. The have 2 different sets of numbers assigned to them. Elements in the same display similar. Some of these groups have special names in addition to their, such as metals, metals, and or gases. The periodic table is arranged according to increasing The periodic table is also made up of 4. The blocks are grouped according to which is filled last. All elements can be divided into 3 groups:,, and. These groupings are made according to and in the periodic table. Title: Sep 17 7:51 PM (18 of 29)

19 color the metals red, the nonmetals yellow, and the metalloids orange. All elements must be colored! Title: Sep 17 8:31 PM (19 of 29)

20 List the properties of the following: Metals (p. 65) Great conductors (of heat & electricity) Malleable Ductile Lustruous (shiny) Nonmetals Often gases or dull, brittle solids Low melting points Found to the Right of the Staircase Forms compounds with metals (NaCl, CaF2) O C O Combines with other nonmetals to form diatomics (O2, N2, H2) Metalloids N Cl Have characteristics of both metals and nonmetals border between metals and nonmetals semiconductors of electricity Sb Te Alkali Metals *Most reactive metals *Very soft *Not found in nature in element form because they are so reactive Alkaline Earth Metals Transition Metals *Very reactive metals *Harder than alkali metals *Still too reactive to be found in nature as an element *Typical Metals Lanthanides and Actinides Halogens Lanthanides called rare earth elements (actually not rare). They're shiny reactive metals. Actinides unstable, radioactive elements. Many of these elements are man made F Noble Gases Ar *Most reactive nonmetals *A group of nonreactive gases. He Kr Title: Sep 17 8:39 PM (20 of 29)

21 3.9 Natural States of Elements Typically we do NOT find elements in pure form (uncombined with other elements). Normally they form compounds readily! What are a few that we have found in pure form? Gold (Au) Platinum (Pt) NOBLE ELEMENTS Silver (Ag) Group 8 Elements (He, Ne, Ar, Kr, Xe, Rn) What are Diatomic Molecules? Solid Elements Liquid Elements Gas Elements Title: Sep 18 1:42 PM (21 of 29)

22 Title: Sep 17 8:35 PM (22 of 29)

23 3.10 Ions Ion definition an element or group of elements with a charge Cation a positive ion Anion a negative ion Title: Sep 18 3:27 PM (23 of 29)

24 Title: Sep 18 3:30 PM (24 of 29) If the atom has a charge, electrons = protons charge.

25 Title: Sep 18 3:34 PM (25 of 29)

26 Complete the following chart Elements to be combined Criss Cross Balanced Formula Magnesium Fluorine Aluminum Bromine Potassium Sulfur Sodium Chlorine Boron Nitrogen Beryllium Phosphorus Aluminum Oxygen Calcium Sulfur Title: Sep 18 3:35 PM (26 of 29)

27 Title: Jul 17 2:33 PM (27 of 29)

28 Bingo Words anion Atom Atomic Number Cation Chemical Formula Compound Electron Ion Isotope Neutron Nucleus Proton Metal Nonmetal Mass Number Nuclear Force uc Title: Sep 21 12:58 PM (28 of 29)

29 Element Symbol Atomic # of # of mass # of Charge Atom/Ion Number Protons Neutrons # electrons 40 Calcium atom Ca Fluorine ion 19 9 F Barium Ion Ba Aluminum Ion Al CarbonAtom 13C Sulfur Atom S Chromium Ion Cr Oxygen Ion O Title: Sep 21 1:43 PM (29 of 29)

30 Attachments role of neutrons Element Quiz Cathode movie rutherford Element song Sodium and chlorine reaction Rutherford 2