ENG 1A Intro to Chemistry - Atomic Weight 2023 PDF

Lesson 1 INTRODUCTION TO CHEMISTRY and ATOMIC MASS Element Compound Atom Nucleus Electron Proton Neutron Atomic Number Mass Number Isotope A.M.U. Atomic Mass Molecular Mass Introduction to Chemistry and Atomic Mass What does Chemistry study? Chemistry studies the composition of matter and the r...

Lesson 1 INTRODUCTION TO CHEMISTRY and ATOMIC MASS Element Compound Atom Nucleus Electron Proton Neutron Atomic Number Mass Number Isotope A.M.U. Atomic Mass Molecular Mass Introduction to Chemistry and Atomic Mass What does Chemistry study? Chemistry studies the composition of matter and the reactions that can occur between different portions of matter. Introduction to Chemistry and Atomic Mass States of matter Classification of matter MATTER Volume Mass Composition Structure Properties Transformations AGGREGATION STATES SOLID (definite Volume and shape) LIQUID (definite Volume and indefinite shape) GASEOUS (indefinite Volume and shape) Introduction to Chemistry and Atomic Mass States of matter Classification of matter MATTER PHYSICALLY HETEROGENEOUS SYSTEMS PHYSICALLY HOMOGENEOUS SYSTEMS CHEMICALLY HETEROGENEOUS SYSTEMS CHEMICALLY HOMOGENEOUS SYSTEMS COMPOUNDS ELEMENTS Introduction to Chemistry and Atomic Mass Elements Gold Iron Silver Compounds Sugar made of: Hydrogen Carbon Oxygen Salt made of: Sodium Chlorine Water made of: Hydrogen Oxygen Introduction to Chemistry and Atomic Mass What is an element? It is a substance made of only one type of atoms, which cannot be divided into simpler substances through chemical reactions. Introduction to Chemistry and Atomic Mass Elements There are a hundred of them; they are ordered by chemists according to their properties which are varying: - periodically, - systematically, - predictably. Introduction to Chemistry and Atomic Mass More than 98 % of the mass of the Earth's crust is composed of the following 13 elements: Oxygen (O) Silicon (Si) Alluminium (Al) Iron (Fe) Calcium (Ca) Sodium (Na) Potassium (K) Magnesium (Mg) Chlorine (Cl) Hydrogen (H) Phosphorus (P) Carbon (C) % in mass 46,1% 25,7% 7,51% 4,70% 3,99% 2,64% 2,40% 1,94% 1,88% 0,580% 0,120% 0,087% Introduction to Chemistry and Atomic Mass Atom [ατομος, from α + τεμνειν] V-IV Century BCE - Leucippus and Democritus Full Immutable Non-generated Eternal It is the fundamental brick of matter Introduction to Chemistry and Atomic Mass Atomic Theory [John Dalton, 1808] 1. All matter is made of indestructible and indivisible microscopic particles, called atoms. 2. All atoms of the same element are identical and have equal mass. 3. Atoms of one element cannot be converted into atoms of other elements. 4. Atoms of one element combine to form a compound only with whole numbers of atoms of other elements. 5. Atoms can neither be created nor destroyed but are transferred whole from one compound to another. Introduction to Chemistry and Atomic Mass Atomic structure Nucleus: actually embodies all the mass of the atom and it is formed by protons (positively charged) and neutrons (no charged), which have very similar mass. Electrons: have almost negligible mass compared to that of protons and neutrons and have negative charge. They rotate around the nucleus. Introduction to Chemistry and Atomic Mass Atom – what size is it? The atom is made of electrons and nucleus. The nucleus is made of protons and neutrons. atomic radius ≈ 10–8 cm = 1 A = 100 pm nuclear radius ≈ 10–13 cm = 10–5 A = 10–3 pm PARTICLE Electron Proton CHARGE -1,60 10–19 C +1,60 10–19 C MASS 9,31 10–31 kg 1,67 10–27 kg Neutron --- 1,67 10–27 kg Introduction to Chemistry and Atomic Mass Atom and Element Mass = Protons + Neutrons All atoms of a certain element contain the same number of protons in the nucleus. Atoms of the same element may contain a different number of neutrons (isotopes). Introduction to Chemistry and Atomic Mass Mass Number and Atomic Number MassAtomic = MassProtons + MassNeutrons Mass number (A, from German Atomgewicht) is equal to the number of neutrons and protons which are present in an atom. Atomic Number (Z, from German Zahl, number) is the number of protons in an atomic nucleus. Introduction to Chemistry and Atomic Mass Iodine 53 126,9045 I (Kr)4d105s25p5 2,5 ±1,+5,+7 Strong Acid Iodine Protons Neutrons Atomic number Mass number Mass ≈ 127 × 1,67 × 10–27 kg 53 74 53 127 Introduction to Chemistry and Atomic Mass 9 18,9984 4,0 1s22s22p5 F -1 Fluorine Mass number 19 53 126,9045 I (Kr)4d105s25p5 2,5 ±1,+5,+7 Strong Acid 17 35,453 Cl (Ne)3s23p5 3,0 ±1,+3,+5,+7 Strong Acid Iodine Chlorine Mass number Mass number 127 35-37 Introduction to Chemistry and Atomic Mass Chlorine 17 35,453 Cl (Ne)3s23p5 3,0 ±1,+3,+5,+7 Strong Acid Chlorine Protons 17 Neutrons 18/20 Atomic number 17 Introduction to Chemistry and Atomic Mass Isotopic Abundance The isotopic abundance is the ratio between the number of atoms of a given isotope of an element and the number of total atoms of the element. The isotopic abundance varies from sample to sample, but it is uniform enough to be considered constant for calculations of the atomic weight of an element. Therefore, the atomic mass reported on the periodic table is a weighted average of the atomic masses of the stable isotopes weighted by their isotopic abundance. Introduction to Chemistry and Atomic Mass Natural Isotopic Abundance Isotope H 2H 12C 13C 14N 15N 16O 17O 18O 28Si 29Si 30Si 32S 33S 34S 35Cl 37Cl 79Br 81Br % Natural Abundance 99.985 0.015 98.89 1.11 99.64 0.36 99.76 0.04 0.2 92.23 4.67 3.10 95.0 0.76 4.22 75.77 24.23 50.69 49.31 Atomic Mass 1.007825 2.0140 12 (by definition) 13.00335 14.00307 15.00011 15.99491 16.99913 17.99916 27.97693 28.97649 29.97376 31.97207 32.97146 33.96786 34.96885 36.96590 78.9183 80.9163 Introduction to Chemistry and Atomic Mass Isotopes and Atomic Mass AElement = i Σi Xi AIsotope where: A is the Atomic Mass of the Elementi, Xi is the Natural Isotopic Abundance, iA is the Atomic Mass of its Isotope i 17 35,453 Cl (Ne)3s23p5 3,0 ±1,+3,+5,+7 Strong Acid Chlorine Mass number 35-37 ACl = 0.7577 · 34,96885 + 0.2423 · 36,9659 = = 35.453 Introduction to Chemistry and Atomic Mass Atomic Mass Unit u, a.m.u. [1961, International Union of Pure and Applied Chemistry (IUPAC)] 1/12 of the mass of Carbon-12 isotope, containing 6 protons and 6 neutrons in the nucleus (1.67 × –27 10 kg) Introduction to Chemistry and Atomic Mass Atomic Mass It is the mass of an atom expressed in a.m.u. The atomic mass unit is also called Dalton (Da), in honor of the English chemist John Dalton, who first suggested in 1803 to use the mass of a Hydrogen atom as a reference when comparing the masses of atoms and chemical compounds. 1 H 1,0079 2,1 1s1 Amphoteric ±1 Hydrogen The mass of a Hydrogen atom is about: 1/12 of the mass of Carbon-12 isotope Introduction to Chemistry and Atomic Mass Some atomic masses a.m.u. (or Da) (atomic weights) H He Li Be B C N O F Ne 1,008 4,003 6,941 9,012 10,811 12,011 14,007 15,999 18,998 20,180 Na Mg Al Si P S Cl Ar K 22,990 24,305 26,981 28,086 30,974 32,066 35,453 39,948 39,098