Atoms, Molecules and Ions Chapter 2

원자, 분자, 이온 원자론 원자의 구조 원자번호, 질량수 및 동위원소 주기율표 분자와 이온 화학식 화합물의 명명 유기화합물의 소개

원자설의 배경 고전적 견해원자설 이전원자설 이전 Law of Conservation of Mass In Reflexions sur le Phlogistique (1783), Antoine Lavoisier Law of the Definite Proportions Joseph-Louise Proust Proust's Law(1799) Pierre Berthollet Law of Multiple Proportions Dalton(1803)

Dalton’s Atomic Theory (1808) 1. Elements are composed of extremely small particles called atoms. 2.All atoms of a given element are identical, having the same size, mass and chemical properties. The atoms of one element are different from the atoms of all other elements. 3.Compounds are composed of atoms of more than one element. In any compound, the ratio of the numbers of atoms of any two of the elements present is either an integer or a simple fraction. 4.A chemical reaction involves only the separation, combination, or rearrangement of atoms; it does not result in their creation or destruction.

2 Dalton’s Atomic Theory Law of Multiple Proportions

8 X 2 Y 16 X8 Y + Law of Conservation of Mass

in 1897, J.J. Thomson, measured mass/charge of e - (1906 Nobel Prize in Physics)

Cathode Ray Tube

e - charge = × C Thomson’s charge/mass of e - = × 10 8 C/g e - mass = 9.10 × g Measured mass of e - (1923 Nobel Prize in Physics)

(Uranium compound)

Thomson’s Model of the Atom "plum pudding" model (1897) Positive charge spread over the entire sphere

1.atoms positive charge is concentrated in the nucleus 2.proton (p) has opposite (+) charge of electron (-) 3.mass of p is 1840 × mass of e - (1.67 × g)  particle velocity ~ 1.4 × 10 7 m/s (~5% speed of light) Rutherford, (1908 Nobel Prize in Chemistry for radioactive decaying) (1909, 1911) Rutherford’s Experiment

(a)The expected result of the Rutherford's a particle scattering experiment, assuming the Thomson’s model. (b) The result of the Rutherford's a particle scattering experiment

Chadwick’s Experiment (1932) (1935 Noble Prize in Physics) H atoms - 1 p; He atoms - 2 p mass He/mass H should = 2 measured mass He/mass H = 4  + 9 Be 1 n + 12 C + energy neutron (n) is neutral (charge = 0) n mass ~ p mass = 1.67 × g

Helium Atom “ 원자가 반지름이 100m 인 운동장 만하다면, 핵은 운동장 중심에 있는 반지름이 수 mm 인 작은 구슬 정도의 크기이다.”

mass p ≈ mass n ≈ 1840 × mass e - Particle Actual mass (kg) Relative mass (amu) Charge (Coulomb) Relative charge Proton, p × × Neutron, n × Electron, e × × × Properties of the proton, the neutron, and the electron

Atomic number (Z) = number of protons in nucleus Mass number (A) = number of protons + number of neutrons = atomic number (Z) + number of neutrons Isotopes are atoms of the same element (X) with different numbers of neutrons in their nuclei X A Z H 1 1 H (D) 2 1 H (T) 3 1 U U Mass Number Atomic Number Element Symbol Atomic number, Mass number and Isotopes

The Isotopes of Hydrogen

6 protons, 8 (14 - 6) neutrons, 6 electrons 6 protons, 5 (11 - 6) neutrons, 6 electrons Q. Number of protons, neutrons and electrons in the isotope of… C 14 6 ? C 11 6 ?

Period Group Alkali Metal Noble Gas Halogen Alkali Earth Metal

Chemistry In Action Natural abundance of elements in Earth’s crust Natural abundance of elements in human body

A molecule is an aggregate of two or more atoms in a definite arrangement held together by chemical forces H2H2 H2OH2ONH 3 CH 4 A diatomic molecule contains only two atoms H 2, N 2, O 2, Br 2, HCl, CO A polyatomic molecule contains more than two atoms O 3, H 2 O, NH 3, CH 4

An ion is an atom, or group of atoms, that has a net positive or negative charge. cation – ion with a positive charge If a neutral atom loses one or more electrons it becomes a cation. anion – ion with a negative charge If a neutral atom gains one or more electrons it becomes an anion. Na 11 protons 11 electrons Na + 11 protons 10 electrons Cl 17 protons 17 electrons Cl - 17 protons 18 electrons

A monatomic ion contains only one atom A polyatomic ion contains more than one atom Na +, Cl -, Ca 2+, O 2-, Al 3+, N 3- OH -, CN -, NH 4 +, NO 3 -

13 protons, 10 (13 – 3) electrons 34 protons, 36 (34 + 2) electrons ?Al ? Se Q. Number of protons, neutrons and electrons in the ion of…

A molecular formula shows the exact number of atoms of each element in the smallest unit of a substance An empirical formula shows the simplest whole-number ratio of the atoms in a substance H2OH2O H2OH2O molecularempirical C 6 H 12 O 6 CH 2 O O3O3 O N2H4N2H4 NH 2

ionic compounds consist of a combination of cations and an anions the formula is always the same as the empirical formula the sum of the charges on the cation(s) and anion(s) in each formula unit must equal zero The ionic compound NaCl

Formula of Ionic Compounds Al 2 O 3 2 × +3 = +63 × -2 = -6 Al 3+ O 2- CaBr 2 1 × +2 = +22 × -1 = -2 Ca 2+ Br - Na 2 CO 3 1 × +2 = +21 × -2 = -2 Na + CO 3 2-

Chemical Nomenclature Ionic Compounds –often a metal + nonmetal –anion (nonmetal), add “ide” to element name BaCl 2 barium chloride K2OK2O potassium oxide Mg(OH) 2 magnesium hydroxide KNO 3 potassium nitrate

Transition metal ionic compounds –indicate charge on metal with Roman numerals FeCl 2 2 Cl - -2 so Fe is +2 iron(II) chloride FeCl 3 3 Cl - -3 so Fe is +3 iron(III) chloride Cr 2 S 3 3 S so Cr is +3chromium(III) sulfide

Molecular compounds nonmetals or nonmetals + metalloids common names H 2 O, NH 3, CH 4, C 60 element further left in periodic table is 1 st element closest to bottom of group is 1 st if more than one compound can be formed from the same elements, use prefixes to indicate number of each kind of atom last element ends in ide

HIhydrogen iodide NF 3 nitrogen trifluoride SO 2 sulfur dioxide N 2 Cl 4 dinitrogen tetrachloride NO 2 nitrogen dioxide N2ON2Odinitrogen monoxide Molecular Compounds TOXIC ! Laughing Gas

An acid can be defined as a substance that yields hydrogen ions (H + ) when dissolved in water. HCl Pure substance, hydrogen chloride Dissolved in water (H + Cl - ), hydrochloric acid An oxoacid is an acid that contains hydrogen, oxygen, and another element. HNO 3 nitric acid H 2 CO 3 carbonic acid H 2 SO 4 sulfuric acid HNO 3

AnionAcid Example prefixsuffixprefixsuffix per-ateper--ic acid perchloric acid (HClO 4 ) -ate-ic acid chloric acid (HClO 3 ) -ite-ous acid chlorous acid (HClO 2 ) hypo-itehypo--ous acid hypochlorous acid (HClO) -idehydro--ic acid hydrochloric acid (HCl) Acid Nomenclature

AcidAnion HClO 4 Perchloric acid ClO 4 - Perchlorate HClO 3 Chloric acid ClO 3 - Chlorate HClO 2 Chlorous acid ClO 2 - Chlorite HClO Hypochlorous acid ClO - Hypochlorite Oxoacids and oxoanions

Don’t confuse with ionBond length Ox no O2O Å0 oxygen O2-O2- super- oxide 1.33 Å-1/2 HO 2 hydrogen superoxide O22-O22- per- oxide 1.49 Å H2O2H2O2 hydrogen peroxide O 2- oxide -2 H2OH2O water(dihydrogen oxide)

A base can be defined as a substance that yields hydroxide ions (OH - ) when dissolved in water. NaOH sodium hydroxide KOH potassium hydroxide Ba(OH) 2 barium hydroxide

Hydrates are compounds that have a specific number of water molecules attached to them. BaCl 2 2H 2 O LiClH 2 O MgSO 4 7H 2 O Sr(NO 3 ) 2 4H 2 O barium chloride dihydrate lithium chloride monohydrate magnesium sulfate heptahydrate strontium nitrate tetrahydrate CuSO 4 5H2O CuSO 4

Organic chemistry is the branch of chemistry that deals with carbon compounds C H H H OH C H H H NH 2 C H H H COH O methanolmethylamineacetic acid Functional Groups( 작용기 )