About the course GENERAL CHEMISTRY. Recommended literature: Chemistry: science of the matter. Responsible for the course: Dr.

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1 About the course GENERAL CHEMISTRY University of Pécs Medical School Academic year Responsible for the course: Dr. Attila AGÓCS Optional course for 2 credit points. To have grade at the and of the semester: two midterm test papers are obligatory to write. 1 st test: 22 October 2 nd test: 10 December 1 2 Recommended literature: McMurry, Fay: Chemistry 4 th ed. Syllabus is avaible at: ETR CooSpace Chemistry: science of the matter Chemistry: the composition, structure and properties of substances and the reactions they undergo. Matter: anything that has mass and occupies space. (synonyms: substance, material) Composition of matter: what is it made of, or what is in it? 3 4

2 Matter Classification of matter by its physical state Physical properties are properties that can be measured and observed without changing the identity of the substance: SOLID LIQUID GAS - State (gas, liquid and solid) - Colour - Melting Point and Boiling Point - Density - Texture - Hardness Also important are: - Mass - Volume but these properties have less to do with distinguishing between substances. 5 Characteristics of states of matter Liquid: fluid, very low compressibility, relatively high density, takes on the shape of the vessel Solid: rigid, very low compressibility, relatively high density sulphur 6 salt water vegetable oil gold iron sand 7 mercury 8

3 Physical change: change in the form of the matter. (e.g. change in the physical state, dissolution of a matter ) Gas: fluid, high compressibility, low density, fills in the avaible space Examples: air bromine vapour helium melting condensation dissolution The quality of the matter does not change. oxygen, hydrogen, carbon dioxide, propane 9 10 Classification of matter by its composition Chemical properties: properties related to the chemical reactivity of the pure substance. How does the pure matter react with some other pure substance? Pure substance: it has a fixed composition and distinct physical and chemical properties. Chemical reaction: new kind of matter(s) forms in a reaction Mixture: a combination of two or more pure substances where each substances retains its chemical identity (its physical and chemical properties). Examples: combustion (reaction with oxigen) precipitate formation The quality of the substance change, a new quality forms. 11 lump-sugar (pure matter) coke (mixture) 12

4 pure substance Matter mixture Element: a substance that can not be decomposed by any chemical reaction into simpler substances. (e.g. sodium, chlorine) Symbol Types: metals, nonmetals, semi-metals element compound homogeneous heterogeneous gold (Au) sulphur (S) oxygen (O) carbon (C) Atomic symbol sugar (C 12 H 22 O 11 ) salt (NaCl) water (H 2 O) carbon dioxide (CO 2 ) Chemical formula solutions air water-sand sulphur-iron Compound: a substance composed of more than one element, chemically combined in a fixed ratio (e.g. sodium chloride, water) Formula Compound Mixture Pure matter Contains at least two different matter Laws of chemistry Mixture: can be separated by physical methods into pure components Homogeneous mixture: that is uniform in their properties throughout given samples. Heterogeneous mixture: a mixture that consist of physically distinct parts with different properties. Law of definite proportions (law of constant composition) A compound, whatever its source, always contains definite or constant proportions of elements by mass. E.g. 18 g of water always contains 2 g of hydrogen and 16 g of oxygen. Law of conservation of mass Mass remains constant during a chemical reaction. E.g. Formation of sodium chloride from sodium and chlorine: If 10 g sodium reacts completely with 15.4 g chlorine 25.4 g salt forms

5 Atomic theory of matter Atomic symbols and chemical formulas John DALTON ( ) Atomic symbol: a one-, two- or three-letter designation used to represent the atoms. Postulates of Dalton s atomic theory: H, C, S, O, Na, Fe, Au 1. All matter is composed of atoms. An atom is an extremely small particle of matter. 2. An element is composed of only one type of atom having the same properties. 3. A compound is composed of atoms of two or more type of elements chemically combined in fixed proportions. 4. Chemical reactions only arrange the way that atoms are combined, the atoms themselves are unchanged. 17 Chemical formula: gives the relative proportion of atoms of the different elements in the substance. H 2, O 2, H 2 O, NaCl, C 12 H 22 O 11, CO 2 18 atom Structure of the atom Atomic number (Z) = number of protons = number of electrons in an atom They determine the chemical properties of the neutral atom. Mass number (A) = number of protons (Z) + number of neutrons (N) nucleus electrons protons neutrons E.g. mass number atomic number 12 6C symbol of carbon Z = 6 A = = 12 How many neutrons are there in the nucleus of a sodium atom? Electron (e - ): negatively charged particle, surrounds the nucleus in shells Proton (p + ): positively charged particle, its mass is 1836 times that of electron Neutron (n): neutral particle, its mass is identical to that of proton mass number atomic number 23 11Na symbol of sodium A = Z + N = 11 + N = 23 N =

6 Isotopes E. g. isotopes of carbon: Atoms with identical atomic number but different mass number. E. g. isotopes of hydrogen: 12 6C the most abundant carbon isotope 1 1H is also called protium, the most abundant hydrogen isotope it is detected in NMR spectroscopy during the structure determination of organic compounds 2 1H or D is called deuterium, component of heavy water, which is used as a moderator in nucler plants 13 is is detected in NMR spectroscopy during the structure 6C determination of organic compounds 14 6C radioactive: is is used in radiocarbon dating. 3 1H or T is called tritium, unstable: radioactive. It is detected in water analysis Isotopes in medicine 60 Co a γ-radiator used in the treatment of certain tumours. Isotopes used in diagnostics as a tracer in PET (positron emission tomography) 15 O or 18 F positron emitters Isotopes used in diagnostics as tracers Isotopes used in diagnostics as a tracer in thyroid gland: 131 I a β- and γ-radiator 123 I a β-radiator 99m Tc a metastable γ-radiator György Hevesy (Nobel prize in 1943) 23 24

7 The mass of the atom Atoms are too small: we need a lot to handle them. mass of p + = g TOO SMALL! Instead of the absolute mass (in gramms) a relative unit is used: atomic mass unit (amu) E. g. dozen = 12 pieces 1 amu = mass of one 12 C 12 = g a dozen of muffins The mass of a helium ( 4 He) atom is: g = amu For atoms: we need much more The mole The mole In 1 mol substance there are particles (pieces) In chemistry: mole = Avogadro s constant Definition: 1 mole contains the same number of particles as many atoms there are in exactly 12 g of 12 C. name of the unit: mole abbreviation: mol 27 28

8 The atomic mass The atomic mass is the mass of 1 mol atoms in gramm. For a given isotope it has the same value as the mass of one atom in amu. The elements are composed of only one type of atom having the same atomic number. In 1 mol atom (element) there can be several different isotopes! The atomic mass is the weighted average of the isotopic masses of the element s naturally occuring isotopes. The atomic mass E. g.: chlorine has two naturally occuring isotopes: isotope 35 Cl 37 Cl Atomic mass of chlorine = isotopic mass (atomic mass of the pure isotope) g/mol g g natural abundance % % % (Mass of 35 Cl) (its abundance) + (Mass of 35 Cl) (its abundance) M Cl = g/mol g/mol = g/mol Periodic Table of the Elements Summary 1. Physical change Chemical change 2. Classification of the matter Matter pure substance mixture element compound homogeneous heterogeneous 3. Atomic symbols and chemical formulas M Cl = g/mol g/mol = g/mol 4. The structure of the atom, isotopes nucleus atom electrons protons neutrons 5. The mole, the atomic mass 31 32