1. Chapter 4 Elements and the Periodic Table Section 1: Introduction to Atoms How did atomic theory develop and change?

2. Chapter 4 Elements and the Periodic Table Section 1: Introduction to Atoms How did atomic theory develop and change? Atomic theory grew as a series of models that developed from experimental evidence. As more evidence was collected, the theory and models were revised.

3. Chapter 4 Elements and the Periodic Table Atomic Theory and Models Dalton thought that atoms were like smooth, hard balls that could not be broken into smaller pieces.

4. Chapter 4 Elements and the Periodic Table Atomic Theory and Models Thomson suggested that atoms had negatively charged electrons embedded in a positive sphere.

5. Chapter 4 Elements and the Periodic Table Rutherford’s Gold Foil Experiment Rutherford was surprised that a few particles were deflected strongly. This led him to propose an atomic model with a positively charged nucleus.

6. Chapter 4 Elements and the Periodic Table Later Atomic Models Through the first part of the twentieth century, atomic models continued to change.

7. Chapter 4 Elements and the Periodic Table Section 1: Introduction to Atoms What is the modern model of the atom?

8. Chapter 4 Elements and the Periodic Table Section 1: Introduction to Atoms What is the modern model of the atom? At the center of the atom is a tiny, massive nucleus containing protons and neutrons. Surrounding the nucleus is a cloudlike region of moving electrons.

9. Chapter 4 Elements and the Periodic Table Modern Model of an Atom This model of a carbon atom consists of positively charged protons and neutral neutrons in a nucleus that is surrounded by a cloud of negatively charged electrons.

10. Chapter 4 Elements and the Periodic Table Particles in an Atom An atom is composed of positively charged protons, neutral neutrons, and negatively charged electrons. Protons and neutrons are about equal in mass. An electron has about 1/2,000 the mass of a proton or neutron.

11. Chapter 4 Elements and the Periodic Table Isotopes Atoms of all isotopes of carbon contain six protons and six electrons, but they differ in their number of neutrons. Carbon- 12 is the most common isotope.

12. Chapter 4 Elements and the Periodic Table End of Section 1: Introduction to Atoms

13. Chapter 4 Elements and the Periodic Table Section 2: Organizing the Elements How did Mendeleev discover the pattern that led to the periodic table?

14. Chapter 4 Elements and the Periodic Table Section 2: Organizing the Elements How did Mendeleev discover the pattern that led to the periodic table? Mendeleev noticed that a pattern of properties appeared when he arranged the elements in order of increasing atomic mass.

15. Chapter 4 Elements and the Periodic Table Section 2: Organizing the Elements How are the elements organized in the modern periodic table?

16. Chapter 4 Elements and the Periodic Table Section 2: Organizing the Elements How are the elements organized in the modern periodic table? The properties of an element can be predicted from its location on the periodic table.

17. Chapter 4 Elements and the Periodic Table The Periodic Table Elements are organized into rows and columns based on their atomic number.

18. Chapter 4 Elements and the Periodic Table The Periodic Table Elements are organized into rows and columns based on their atomic number.

19. Chapter 4 Elements and the Periodic Table The Periodic Table Elements are organized into rows and columns based on their atomic number.

20. Chapter 4 Elements and the Periodic Table Finding Data on Elements Each square in the periodic table lists four pieces of information: an element’s atomic number, chemical symbol, name, and atomic mass.

21. Chapter 4 Elements and the Periodic Table End of Section 2: Organizing the Elements