The Periodic Table

Chemical Bonds Covalent Bonds Bonds formed when atoms share electrons. Ionic Bonds Bonds formed by the attraction of oppositely charged ions. Metals tend to lose electrons and form positive ions called Cations. Nonmetals tend to gain electrons and form negative ions called Anions. Covalent Bonds Bonds formed when atoms share electrons. Typically forms when two nonmetals bond. 31

Binary Ionic Compounds 1. The cation is always named first and the anion second. 2. A monatomic cation takes its name from the name of the parent element. 3. If the metal in the compound can form more than one type of ion, then specify which charge with a Roman numeral. 4. A monatomic anion is named by taking the root of the element name and adding –ide. 42

Polyatomic Ions you must know

Binary Covalent Compounds 1. The first element in the formula is named first, using the full element name. 2. The second element is named as if it were an anion. 3. Prefixes are used to denote the numbers of atoms present for both the first and second element. 4. EXCEPTION: prefix mono- is NOT used for naming the first element. 48

Early History of Chemistry Democritus (an ancient Greek philosopher/scientist) is credited as one of the first to consider the presence of atoms in matter. Atom derives from the word atomos which means indivisible. Alchemy dominated for 2000 years and few advances were made. However, alchemists did move the study of nature from the realm of pure thought to the concept of observation and experimentation. Robert Boyle (mid to late 1600s) was the first “chemist” to perform quantitative experiments. 3

Important Laws of Chemistry Law of conservation of mass (Lavoisier 1783): Mass is neither created nor destroyed in a chemical reaction. (mass of reactants = mass of products) Law of definite proportion (Proust): Elements combine in constant proportions to form a given compound. 5

Dalton’s Atomic Theory (1808) Elements of mater consist of characteristics particles. Atoms of a given element are identical to each other. Atoms are indivisible. There are as many kinds of atoms as there are elements. Atoms of one element cannot be converted into atoms of another. Atoms cannot be created or destroyed, merely rearranged. Compounds are formed when atoms of 2 or more elements combine in a fixed ratio. 8

J. J. Thomson (1897) Using cathode-ray tubes, Thomson discovered the following: All matter include negatively charged particles we now call electrons Determined the charge-to-mass ratio of an electron. Since atoms are known to be neutral, positively charged particles must also exist within the atoms. Developed the Raisin-Bun Model for an atom. (a.k.a. the plum-pudding model) 17

Cathode-Ray Tube Experiment Draw a rough sketch of J.J. Thomson’s cathode ray experiment. Be sure you can explain how his results lead to the discovery of the electron. 18

(Draw a rough sketch of Millikan’s experiment below.) Robert Millikan (1909) Performed experiments involving charged oil drops. (Draw a rough sketch of Millikan’s experiment below.) Determined the magnitude of the charge on a single electron. Calculated the mass of the electron. 19

Ernest Rutherford (1911) Sketch Rutherford’s Gold-Foil Experiment. Be sure to illustrate the somewhat surprising results. 22

Ernest Rutherford (1911) Conclusions reached by Rutherford At the atomic level, matter consists of mostly empty space. At the center of the atom is a tiny, positively charged nucleus. The negatively charged electrons travel around the nucleus. 22

Modern View of the Atom The atom contains: Electrons – travel outside nucleus; negative charge; very small mass Protons – in nucleus; positive charge; comparatively much more massive. Neutrons – in nucleus; no charge; same mass as proton. The nucleus is: Small compared with the overall size of the atom. Extremely dense; accounts for almost all of the atom’s mass 23

Isotopes Atoms with the same number of protons but different numbers of neutrons. Show almost identical chemical properties; chemistry of atom is due to its electrons. In nature most elements contain mixtures of isotopes. 26

Symbolic Notation for Isotopes Isotopes are identified by: Atomic Number (Z) – number of protons Mass Number (A) – number of protons plus number of neutrons 28