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Chapter 2 Atoms and Elements Dr. S. M. Condren.

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1 Chapter 2 Atoms and Elements Dr. S. M. Condren

2 Dalton’s Atomic Theory
Postulates proposed in 1803 know for first exam Dr. S. M. Condren

3 Dalton’s Atomic Theory
Postulate 1 An element is composed of tiny particles called atoms. All atoms of a given element show the same chemical properties. Dr. S. M. Condren

4 Dalton’s Atomic Theory
Postulate 2 Atoms of different elements have different properties. Dr. S. M. Condren

5 Dalton’s Atomic Theory
Postulate 3 Compounds are formed when atoms of two or more elements combine. In a given compound, the relative number of atoms of each kind are definite and constant. Dr. S. M. Condren

6 Dalton’s Atomic Theory
Postulate 4 In an ordinary chemical reaction, no atom of any element disappears or is changed into an atom of another element. Chemical reactions involve changing the way in which the atoms are joined together. Dr. S. M. Condren

7 Structure of the Atom protons Composed of: protons neutrons electrons
found in nucleus relative charge of +1 relative mass of amu Dr. S. M. Condren

8 Structure of the Atom neutrons Composed of: protons neutrons electrons
found in nucleus neutral charge relative mass of amu Dr. S. M. Condren

9 Structure of the Atom electrons Composed of: protons neutrons
found in electron cloud relative charge of -1 relative mass of amu Dr. S. M. Condren

10 ATOM COMPOSITION The atom is mostly empty space
protons and neutrons in the nucleus. the number of electrons is equal to the number of protons in a neutral atom. electrons in space around the nucleus. extremely small. One teaspoon of water has 3 times as many atoms as the Atlantic Ocean has teaspoons of water. Dr. S. M. Condren

11 Radioactivity Alpha – helium-4 nucleus Ra226  Rn222 + He4(a)
Beta – high energy electron U239  Np b-1 Gamma – energy resulting from transitions from one nuclear energy level to another Ni60*  Ni g Dr. S. M. Condren

12 Penetrations of Radioactive Emissions
Dr. S. M. Condren

13 Isotopes & Their Uses 9943Tc Emits gamma rays
Heart scans with radioactive technetium-99. 9943Tc Emits gamma rays Dr. S. M. Condren

14 The modern view of the atom was developed by Ernest Rutherford (1871-1937).
Dr. S. M. Condren

15 Rutherford’s Model of the Atom
atom is composed mainly of vacant space all the positive charge and most of the mass is in a small area called the nucleus electrons are in the electron cloud surrounding the nucleus Dr. S. M. Condren

16 Nucleus If nucleus is 1” The atom would be 1.5 miles in diameter
Dr. S. M. Condren

17 Ions Ion cations anions ionic compounds
electrostatically charged atom or group of atoms cations positive ions anions negative ions ionic compounds combination of cations and anions zero net charge Dr. S. M. Condren

18 Atomic number, Z the number of protons in the nucleus
the number of electrons in a neutral atom the integer on the periodic table for each element 13 Atomic number Al Atom symbol 26.981 Atomic weight Dr. S. M. Condren

19 Dr. S. M. Condren

20 Imaging Dr. S. M. Condren

21 Which best represents the poles?
Dr. S. M. Condren

22 Quantum Corral
Dr. S. M. Condren

23 Mass Number, A C atom with 6 protons and 6 neutrons is the mass standard = 12 atomic mass units (u) Mass Number (A) = # protons + # neutrons A boron atom can have A = 5 p n = 10 u Dr. S. M. Condren

24 Isotopes atoms of the same element which differ in the number of neutrons in the nucleus designated by mass number Dr. S. M. Condren

25 Isotopes of Hydrogen H-1, 1H, protium
1 proton and no neutrons in nucleus only isotope of any element containing no neutrons in the nucleus most common isotope of hydrogen Dr. S. M. Condren

26 Isotopes of Hydrogen H-2 or D, 2H, deuterium
1 proton and 1 neutron in nucleus Dr. S. M. Condren

27 Isotopes of Hydrogen H-3 or T, 3H, tritium
1 proton and 2 neutrons in nucleus radioactive electron antineutrino Dr. S. M. Condren

28 The radioactive isotope 14C has how many neutrons? 6, 8, other
Dr. S. M. Condren

29 protons, neutrons, electrons
The identity of an element is determined by the number of which particle? protons, neutrons, electrons Dr. S. M. Condren

30 Mass Spectrometer a simulation is available at
Dr. S. M. Condren

31 Mass spectrum of C6H5Br Dr. S. M. Condren

32 Atomic Masses and Isotopic Abundances
natural atomic masses = SUM[(atomic mass of isotope) *(fractional isotopic abundance)] Dr. S. M. Condren

33 Example: Chlorine has two isotopes, Cl-35 and Cl-37, which have masses of and amu, respectively. The natural atomic mass of chlorine is amu. What are the percent abundances of the two isotopes? let x = fraction Cl-35 y = fraction Cl-37 x + y = 1 y = 1 - x (AW Cl-35)(fraction Cl-35) + (AW Cl-37)(fraction Cl-37) = Thus: *x *y = *x *(1-x) = x = <=> % Cl-35 Thus % Cl-37 Dr. S. M. Condren

34 Molar Mass-Molecular Weight
Sum atomic masses represented by formula atomic masses => gaw molar mass => MM Dr. S. M. Condren

35 Example What is the molar mass of ethanol, C2H5O1H1?
MM = 2(gaw)C + (5 + 1)(gaw)H + 1(gaw)O = 2(12.011)C + 6( )H + 1( )O = = g/mol Significant figures rule for multiplication Significant figures rule for addition Sequence – multiplication then addition, apply significant figure rules in proper sequence Dr. S. M. Condren

36 The Mole a unit of measurement, quantity of matter present
Avogadro’s Number 6.022 x 1023 particles Latin for “pile” Dr. S. M. Condren

37 One Mole of each Substance
Clockwise from top left: 1-Octanol, C8H17OH; Mercury(II) iodide, HgI2; Methanol, CH3OH; and Sulfur, S8. Dr. S. M. Condren

38 Example How many moles of carbon dioxide molecules are there in 10.00g of carbon dioxide? MM = 1(gaw)C + 2(gaw)O = g/mol #mol CO2 = (10.00g) / / (1 mol/44.01g) = mol Dr. S. M. Condren

39 Mendeleev’s Periodic Table
Missing elements: 44, 68, 72, & 100 amu Dr. S. M. Condren

40 Properties of Ekasilicon
Dr. S. M. Condren

41 Modern Periodic Table the elements are arranged according to increasing atomic numbers Dr. S. M. Condren

42 Periodic Table of the Elements
Dr. S. M. Condren

43 Organization of Periodic Table
period - horizontal row group - vertical column Family Names Group IA alkali metals Group IIA alkaline earth metals Group VIIA halogens Group VIIIA noble gases transition metals inner transition metals lanthanum series rare earths actinium series trans-uranium series Dr. S. M. Condren

44 Dr. S. M. Condren

Allotropes of C Dr. S. M. Condren

46 Dr. S. M. Condren


ELEMENTS THAT EXIST AS POLYATOMIC MOLECULES S8 sulfur molecules White P4 and polymeric red phosphorus Dr. S. M. Condren

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