Chapter 4 Atomic Structure

Defining the Atom Early Models of the Atom Democritus – Greek philosopher suggested the existence of the atom around 400 BC Atoms are _____________________ Idea lacked ______________ support Idea challenged by ________________

Dalton – early 1800’s (2000 yrs. after Democritus) Used experiments (Scientific Method) Studied the nature of atoms & ratios in which elements combine in chemical reactions Dalton’s Atomic Theory: page 102

1 - All elements are composed of _____________________________________ 4.1 1 - All elements are composed of _____________________________________ According to Dalton’s atomic theory, an element is composed of only one kind of atom, and a compound is composed of particles that are chemical combinations of different kinds of atoms. a) Atoms of element A are identical. b) Atoms of element B are identical, but differ from those of element A. c) Atoms of elements A and B can physically mix together. d) Atoms of elements A and B can chemically combine to form a compound. Interpreting Diagrams How does a mixture of atoms of different elements differ from a compound?

4.1 2 - Atoms of the same element are _________. The atoms of any one element are ___________ from those of any other element. According to Dalton’s atomic theory, an element is composed of only one kind of atom, and a compound is composed of particles that are chemical combinations of different kinds of atoms. a) Atoms of element A are identical. b) Atoms of element B are identical, but differ from those of element A. c) Atoms of elements A and B can physically mix together. d) Atoms of elements A and B can chemically combine to form a compound. Interpreting Diagrams How does a mixture of atoms of different elements differ from a compound?

4.1 3 - Atoms of different elements can _________mix together or can _______________________________________. According to Dalton’s atomic theory, an element is composed of only one kind of atom, and a compound is composed of particles that are chemical combinations of different kinds of atoms. a) Atoms of element A are identical. b) Atoms of element B are identical, but differ from those of element A. c) Atoms of elements A and B can physically mix together. d) Atoms of elements A and B can chemically combine to form a compound. Interpreting Diagrams How does a mixture of atoms of different elements differ from a compound?

4.1 4 - Chemical reactions occur when atoms are _________________________. Atoms of one element are _____________________________________in a chemical reaction. According to Dalton’s atomic theory, an element is composed of only one kind of atom, and a compound is composed of particles that are chemical combinations of different kinds of atoms. a) Atoms of element A are identical. b) Atoms of element B are identical, but differ from those of element A. c) Atoms of elements A and B can physically mix together. d) Atoms of elements A and B can chemically combine to form a compound. Interpreting Diagrams How does a mixture of atoms of different elements differ from a compound? Scientists used a scanning tunneling microscope to generate this image of iron atoms, shown in blue. The radius of this circle of atoms is just 7.13 × 10-9 m.

Atoms are defined today as _____________________________________ Atoms today are observable with scanning tunneling microscope Dalton’s work stimulated much scientific research into the structure of the atom

Page 103, Section assessment # 1 to 7, skip 6 READ pages 104, 105 summarize JJ Thomson’s use of cathode ray tube

Structure of the Nuclear Atom Subatomic Particles Electrons JJ Thomson used cathode ray tube to discover ___________, 1897 Figures 4.4, 4.5 Concluded that electrons must be parts of atoms of all elements Millikan – electron ___________________

Protons E Goldstein used cathode ray tube and found rays traveling in opposite direction to cathode ray, 1886 Concluded that rays were made of ____________________ Protons have mass __________________

Table 4.1 – Properties of Subatomic Particles Neutrons _______________ confirmed the existence of neutrons, 1932 Particle with ____ charge, mass equal to ___________ Table 4.1 – Properties of Subatomic Particles

4.2 Subatomic Particles Table 4.1 summarizes the properties of electrons, protons, and neutrons.

The Atomic Nucleus Scientists tried to answer the question, How are subatomic particles put together in the atom? JJ Thomson – the ‘plum pudding’ model:

The Atomic Nucleus Rutherford’s Gold-Foil Experiment 4.2 In 1911, Rutherford and his coworkers at the University of Manchester, England, directed a narrow beam of alpha particles at a very thin sheet of gold foil.

E Rutherford – student of Thomson Gold foil experiment – figure 4.7 In the plum pudding model, alpha particles should pass through the foil with slight deflections caused by the positive charge spread throughout the gold atoms Results showed that ____________________________________

Rutherford’s new theory: atom is mostly _______________ Positive charge is concentrated in small region – ____________ Nuclear atom – small nucleus with protons and neutrons; electrons occupy most of the volume

Page 108, Section Assessment, # 8 -14 Page 110, Vocabulary

Distinguishing Among Atoms Atomic Number # of _____________ Identifies an atom All atoms are neutral, therefore, ______________________________ Table 4.2 Page 111, Practice Problems #15, 16

4.3 Atomic Number

Page 112, Sample Problem 4.1, Practice Problems # 17 & 18 Mass Number Total # of ________ + _____________ # neutrons = ______ # - _________ # Atomic notation 2 forms, page 111, last sentence Page 112, Sample Problem 4.1, Practice Problems # 17 & 18

Mass Number 4.3 Au is the chemical symbol for gold. Au is the chemical symbol for gold. Applying Concepts How many electrons does a gold atom have?

for Sample Problem 4.1

Page 113, Conceptual Problem 4.2, Practice Problems # 19 & 20 Isotopes Same #______ but different # ________, therefore, different ________ # Figure 4.9 Isotopes of Hydrogen: page 113 Page 113, Conceptual Problem 4.2, Practice Problems # 19 & 20

Atomic Mass Amu – atomic mass unit, unit that measures mass of atoms and subatomic particles 1 amu = 1/12 mass of carbon-12 ( mass of carbon-12 is assigned to be 12 amu Proton mass = neutron mass = 1 amu = 1.67 x 10-24 grams

Electron mass = 9.11 x 10-28 grams Most elements occur as a mixture of 2 or more isotopes Atomic mass is a weighted average atomic mass that reflects both the mass and ___________________ of each isotope Table 4.3

Page 115, Sample Problem Calculate average atomic mass: Mass of each isotope x % abundance Add products Page 115, Sample Problem

Periodic Table Arrangement of elements based on _________________________ Arranged in order of increasing atomic ______________ Period – horizontal row – properties vary as you move across the period, and repeat in each row Group – vertical column – elements in groups have similar chemical and physical properties

Page 119, Section Assessment, # 25 – 33 Chapter 4 Assessment Page 122-123, #34-73, skip 38,62,67,68 Page 124, #74, 79, 80 Standardized Test Prep page 125, # 1 - 9