This week: What are atoms made of? How do you name compounds and molecules? If you have had chem 10, the Physical Science division really needs FAL leaders. Please see me after class Dalton s atomic theory 1806 A good theory: Explains all available data Predicts the future Is usually ignored/disgraced for a while Known natural laws in 1806: Law of conservation of mass: Lavoisier 1785 Law of constant composition: 1700 s Law of multiple proportions: Dalton Natural Law: Statement of WHAT happens, not why Discovery of electrons The size of an atom Figure 2.4 Figure 2.12 1
Sub atomic particles Amu: atomic mass unit 1 amu = 1.66054 x 10 24 g A specific carbon atom has exactly 12 amu All else is relative Particle Proton Electron Charge +1 1 Mass (g) 1.673 x10 24 9.11 x10 28 Mass (amu) 1.007 5.5 x10 4 Table 2.1 neutron 0 1.675 x10 24 1.008 Atoms are really small! Atoms are really small Atomic Force Microscopy Heaviest atom is only 4x10 22 g Only 1x10 10 m in diameter Can t see with optical microscopes Gnat sized nucleus here, outer atom at Hwy 1 Mass spectrometer Mass spectrum of Cl Figure 2.14 Figure 2.13 Mass spec 2
Average atomic mass similar to GPA calculation 3 unit class = C (2 grade points) 5 unit class = A (4 grade points) Does GPA = 3? Atomic symbols Atomic number = # of protons in nucleus. Mass number = # of p plus n in nucleus At the Earth s surface, 98.93% C with 12 amu 1.07% C with 13 amu Calculate the average mass of C atoms Isotopes have the same # p but different # n. # of protons define the element 11 6 C 12 6 C 13 6 C 14 6 C Concept Check-isotopes Can two atoms have the same mass but be different elements? Cu-63 and Zn-63 px Complete atomic Isotope symbols symbols m ± X is atomic symbol p is atomic number (# of??) m is mass number (# of?? +??) Charge shows result of electrons lost or gained Write atomic symbol for: P, Zn, common ion of Na On Periodic Table 3 Li 6.941 Atomic # Atomic symbol Atomic mass Concept check: atomic symbols How many protons, neutrons and electrons in Phosphorus-31? What is the full atomic symbol for P-31 if it has gained 3 e How many protons, neutrons and electrons in Pu-239? What is the full atomic symbol for a 2 + ion that has 35 n and 28 e? 3
Discovery Radioactivity of Radioactivity Three types of radiation were discovered in the early 1900 s by α particles He nuclei β particles electrons γ rays high Energy X-rays Marie Curie Henri Becquerel Ernest Rutherford Figure 2.8 Radioactivity is the process of nuclei changing spontaneously into other nuclei Nuclear decay is not affected by Temp, Pressure or time Relative Penetration power α β γ Radiation is useful for sterilization, killing cancer cells, and imaging tissues 4
Types of compounds Compounds are two or more atoms bonded together. The chemical formula of a compound indicates which atoms are found in the molecule, and in what proportion they are found. Compounds consisting of MOLECULES are molecular compounds. Compounds consisting of IONS are ionic compounds Molecules that contain two atoms of same element bonded together are called diatomic molecules. Molecules and Molecular Compounds diatomics Ionic Compounds Ions are charged atoms or molecules Ionic compounds (such as NaCl) are usually formed between metals and nonmetals. Prediciting Predicting charge Predicting Ionic Charge Figure 2.23 Figure 2.22 Naming ionic compounds Cation (+ ion) name goes first elemental cations are named as element Naming oxo-anion Inorganic Compounds Anion ( ion) goes second replace suffix of element with ide GaAs gallium + arsenic = gallium arsenide examples from PT Follow same rules for Polyatomic ions Tranisition metal compounds: use Roman numerals Figure 2.26 5
Molecular compounds Molecular compounds exist as individual molecules Molecules stay intact when going from solid to liquid to gas Molecular formula: actual ratio of elements in molecule C 6 H 12 O 6 Empirical formula: smallest whole # ratio of elements CH 2 O Rules for naming molecular compounds More metallic element s name comes first Metallic character increases going down or left When in doubt, put carbon first, or oxygen last Add ide to the 2 nd element s name Use Greek prefixes to show how many atoms are in the compound Drop one letter of a-o or o-o, but not i i Example carbon monoxide, not carbon monooxide Molecular compound prefixes Examples A compound with 2 N and 3 F Nitrogen is to the left, so elements are in order: Nitrogen fluoride Add prefixes: dinitrogen trifluoride Examples Concept Check Name: N 8 Cl 7 CBr 4 S 7 O 5 What is formula of hexaphosporus pentaselenide? What is name of O 2 F 5? 6
Naming Inorganic acids Acids: a special class of compound, Have H in formula Names of acids are related to the names of anions: -ide becomes hydro-.-ic acid; -ate becomes -ic acid; -ite becomes -ous acid. examples g a c i d s Figure 2.28 Some Simple Organic Compounds Alkanes Organic chemistry: the study of the chemistry of carbon compounds. Alkanes contain only C and H and are called hydrocarbons. The names of alkanes all end in the suffix ane. Alkanes are named according to the number of C atoms in their backbone chain: Methane has one C atom (CH 4 ) Ethane has two C atoms (CH 3 CH 3 ) Propane has three C atoms (CH 3 CH 2 CH 3 ), etc. Know methane through hexane: CH 4 CH 3 CH 3 CH 3 CH 2 CH 3 CH 3 CH 2 CH 2 CH 3 CH 3 CH 2 CH 2 CH 2 CH 3 CH 3 CH 2 CH 2 CH 2 CH 2 CH 3 What is name of this compound: CH 3 CH 2 Cl Ionic examples Make and name ionic compounds: Na and N Cu 2+ and NO 3 Co 3+ and CO 2 3 K and CN Ca and PO 4 3 Sr and MnO 4 Zn and SO 3 2 Concept Check: Write formulas for the following compounds Iron (II) hydride Lead (IV) phosphate Manganese (II) perchlorate Sodium hypochlorite Beryllium hydroxide Aluminum nitrite Lithium oxalate Magnesium cyanide Chromium (VI) bicarbonate Zinc sulfite 7