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Chapter 4 Atomic Structure. Defining the Atom Early Models of the Atom Democritus – Greek philosopher suggested the existence of the atom around 400 BC.

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Presentation on theme: "Chapter 4 Atomic Structure. Defining the Atom Early Models of the Atom Democritus – Greek philosopher suggested the existence of the atom around 400 BC."— Presentation transcript:

1 Chapter 4 Atomic Structure

2 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 ________________

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

4 1 - All elements are composed of _____________________________________ 4.1

5 2 - Atoms of the same element are _________. The atoms of any one element are ___________ from those of any other element. 4.1

6 3 - Atoms of different elements can _________mix together or can _______________________________________. 4.1

7 4 - Chemical reactions occur when atoms are _________________________. Atoms of one element are _____________________________________in a chemical reaction. 4.1

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

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

10 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 ___________________

11 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 __________________

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

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

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

15 The Atomic Nucleus – Rutherfords Gold-Foil Experiment 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. 4.2

16 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 ____________________________________

17 Rutherfords 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

18 Page 108, Section Assessment, # Page 110, Vocabulary

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

20 Atomic Number 4.3

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

22 Mass Number Au is the chemical symbol for gold. 4.3

23 for Sample Problem 4.1

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

25 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 grams

26 –Electron mass = 9.11 x 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

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

28 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

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


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