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Atoms, Molecules, and Ions. Conservation of Mass. Dalton’s Atomic Theory 01. Robert Boyle (1627–1691): Provided evidence for the atoms and defined the nature of an element. Joseph Priestley (1733–1804): Isolated oxygen gas from decomposition of mercury(II) oxide.

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Dalton s atomic theory 01
Dalton’s Atomic Theory 01

  • Robert Boyle (1627–1691): Provided evidence for the atoms and defined the nature of an element.

  • Joseph Priestley (1733–1804): Isolated oxygen gas from decomposition of mercury(II) oxide.

  • Antoine Lavoisier (1743–1794): Showed that mass of products is exactly equal to the mass of reactants.

Chapter 02


Dalton s atomic theory 02
Dalton’s Atomic Theory 02

  • Law of Mass Conservation: Mass is neither created nor destroyed in chemical reactions.

  • Law of Definite Proportions: Different samples of a pure chemical substance always contain the same proportion of elements by mass.

Chapter 02


Dalton s atomic theory 03
Dalton’s Atomic Theory 03

  • John Dalton (1766–1844): Proposed explanations for the laws of mass conservation and definite proportions.

Flash Animation - Click to Continue

Chapter 02



Dalton s atomic theory 041
Dalton’s Atomic Theory 04

  • Law of Multiple Proportions:

  • When two elements form two different compounds, the mass ratios are related by small whole numbers.

Chapter 02


Dalton s atomic theory 05
Dalton’s Atomic Theory 05

  • Nitrogen & oxygen combine to form NO or NO2:

    • In NO the N:O mass ratio is 7:8

    • In NO2 the N:O mass ratio is 7:16

  • Hydrogen & oxygen combine to form H2O or H2O2:

    • In H2O the H:O mass ratio is 1:8

    • In H2O2 the H:O mass ratio is 1:16

Chapter 02


Dalton s atomic theory 06
Dalton’s Atomic Theory 06

  • Methane and ethane are both constituents of natural gas. A sample of methane contains 11.40 g of carbon and 3.80 g of hydrogen, whereas a sample of ethane contains 4.47 g of carbon and 1.118 g of hydrogen. Show that the two substances obey the law of multiple proportions.

Chapter 02


The structure of atoms 01
The Structure of Atoms 01

  • Cathode-Ray Tube (Thomson, 1856–1940):

  • Cathode raysconsist of tinynegativelycharged particles, now calledelectrons.

Chapter 02


The structure of atoms 02
The Structure of Atoms 02

  • Deflection of electron depends on three factors:

    • Strength of electric or magnetic field

    • Size of negative charge on electron

    • Mass of the electron

  • Thomson calculated the electron’s charge to mass ratio as 1.758820 x 108 Coulombs per gram.

Chapter 02


The structure of atoms 03
The Structure of Atoms 03

  • Oil Drop Experiment (Millikan, 1868–1953): Applied a voltage to oppose the downward fall of charged drops and suspend them.

  • Voltage on plates place 1.602176 x 10-19 C of charge on each oil drop.

  • Millikan calculated the electron’s mass as 9.109382 x 10-28 grams.

Chapter 02


The structure of atoms 05
The Structure of Atoms 05

  • Discovery of Nucleus (Rutherford, 1871 – 1937):

  • Rutherford irradiatedgold foil with a beamof alpha () particlesto search for positivecharged particles.

Chapter 02


The structure of atoms 051
The Structure of Atoms 05

Discovery of Nucleus (Rutherford, 1871–1937):

Rutherford irradiatedgold foil with a beamof alpha () particlesto search for positivecharged particles.

Atom must be mostly empty space except for a central positive mass concentration.

Chapter 02


The structure of atoms 04
The Structure of Atoms 04

  • Structure of the Atom:

Chapter 02



The structure of atoms 06
The Structure of Atoms 06

  • Isotopes: Atoms with identical atomic numbers, but different mass numbers.

  • Average Isotopic Mass: A weighted average of the isotopic masses of an element’s naturally occurring isotopes.

  • Atomic Mass: A weighted average of the isotopic masses of an element’s naturally occurring isotopes.

Chapter 02


The structure of atoms 07

75

75

Se

Se

34

34

The Structure of Atoms 07

  • The isotope is used medically for diagnosis of pancreatic disorders. How many protons, neutrons, and electrons does an atom of have?

  • An atom of element X contains 47 protons and 62 neutrons. Identify the element, and write the symbol for the isotope in the standard format.

Chapter 02


The structure of atoms 08

37

35

Cl

Cl

17

17

The Structure of Atoms 08

  • Chlorine has two naturally occurring isotopes: with an abundance of 75.77% and an isotopic mass of 34.969 amu, and with an abundance of 24.23% and an isotopic mass of 36.966 amu. What is the atomic mass of chlorine?

Chapter 02




Atoms molecules and ions 01
Atoms, Molecules, and Ions 01

  • Covalent Bonding (Molecules):The most common type of chemical bond is formed when two atoms share some of their electrons.

Chapter 02


Atoms molecules and ions 02
Atoms, Molecules, and Ions 02

  • Ionic Bonding (Ionic Solids):These are formed by a transfer of one or more electrons from one atom to another.

Chapter 02


Atoms molecules and ions 03
Atoms, Molecules, and Ions 03

  • Which of the following drawings represents an ionic compound, and which a molecular compound?

Chapter 02


Atoms molecules and ions 04
Atoms, Molecules, and Ions 04

  • Naming Binary Ionic Compounds:

  • Identify the positive ion and then the negative ion.

  • The positive ion uses its elemental name.

  • The negative ion substitutes the second half of its elemental name with –ide.

  • Do not use Greek prefixes such as mono–, di–, or tri–.

Chapter 02




Atoms molecules and ions 07

Main Group Cations and Anions.

Atoms, Molecules, and Ions 07

  • Ions combine to form neutral compounds.

  • Examples:

    • Na+ and Cl– combine to form NaCl.

    • Ca2+ and Cl– combine to form CaCl2.

    • Al3+ and Cl– combine to form AlCl3.

Chapter 02



Atoms molecules and ions 09
Atoms, Molecules, and Ions 09

  • Naming Binary Molecular Compounds:

  • The more cationlike element uses its elemental name.

  • The more anionlike element substitutes the second half of its elemental name with –ide.

  • Use the Greek prefixes to express the number of each element present.

Chapter 02



Atoms molecules and ions 11
Atoms, Molecules, and Ions 11

  • If the green spheres represent cations, and the blue represent anions, which of the formulas are consistent with the figure? (a) LiBr (b) NaNO2 (c) CaCl2 (d) K2CO3 (e) Fe2(SO4)3

Chapter 02



Atoms molecules and ions 13
Atoms, Molecules, and Ions 13

  • Name the following acids:

    • (a) HBrO(aq)(b) HCN(aq)(c) HIO4(aq)(d) HBrO2(aq)(e) H2CrO4(aq)

Chapter 02


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