Unit 6, Chapter 18

1. Unit 6, Chapter 18 Integrated Science

2. Unit Six: Properties of Matter Chapter 18 Atoms and Elements • 18.1 Atomic Structure • 18.2 Comparing Atoms • 18.3 The Periodic Table of Elements

3. Chapter 18 Learning Goals • Use indirect measurement to determine the radius of a circle. • Build models of atoms. • Research one of the historical atomic models. • Understand how atoms of each element differ. • Describe the forces that hold an atom together. • Use the concept of electron shells to arrange electrons in atomic models. • Understand how elements are organized in the periodic table. • Use the periodic table to identify the atomic number and mass numbers of each element. • Calculate the numbers of protons and neutrons in each stable isotope of an element.

4. neutrons nucleus periodic table of elements protons strong nuclear force subatomic particles valence electrons Chapter 18 Vocabulary Terms • atomic mass electrons • atomic mass units • atomic number • atomic theory • energy levels • group of elements • isotopes • mass number

5. 18.1 Atomic Structure • All matter is formed from atoms. • If broken apart, almost all atoms contain three smaller particles called protons, neutrons, and electrons. • Protons and neutrons cluster together in the atom’s center, called the nucleus.

6. Atoms and molecules are called the building blocks of matter. Atoms are very small. Subatomic particles have charge and mass: proton (p+) = 1 amu neutron (n0) = 1 amu electron (e-) = 1/2000 amu Most of the atom is empty space because almost all of the mass of an atom is concentrated in its nucleus. 18.1 Atomic Structure

7. 18.1 Changing model of the atom John Dalton's Atomic Theory 1808 • Each element is composed of extremely small particles called atoms. • All atoms of a given element are identical. • Atoms of different elements have different properties, including mass and chemical reactivity. • Atoms are not changed by chemical reactions, but merely rearranged into different compounds. • Compounds are formed when atoms of more than one element combine. • A compound is defined by the number, type (element), and proportion of the constituent atoms.

8. 18.1 Changing model of the atom • Dalton pictured the atom as a small hard sphere.

9. 18.1 Changing model of the atom • The Thompson model suggested negative electrons were embedded in a positive sphere.

10. 18.1 Changing model of the atom • Bohr's model showed electrons moving around the nucleus in fixed orbits.

11. 18.1 Changing model of the atom • Schrödinger's mathematical model demonstrated that the electron position could be predicted, but not pinpointed exactly.

12. Key Question: How was the size of an atom's nucleus discovered ? 18.1 Atomic Structure *Read text section 18.1 BEFORE Investigation 18.1

13. 18.2 Comparing Atoms • The number of protons determines an element.

14. 18.2 Mass Number • The total number of protons and neutrons in the nucleus of an atom is called the mass number.

15. 18.2 Isotopes • Isotopes are atoms of the same element that have different numbers of neutrons. • These are all isotopes of hydrogen.

18. Key Question: What are atoms and how are they put together? 18.2 Comparing Atoms *Read text section 18.2 BEFORE Investigation 18.2

19. Elements are made up of only one kind of atom. Compounds are made up of combinations of atoms. Elements that are part of the same group act alike. 18.3 The Periodic Table of Elements

20. Dimitri Mendeleev (1834- 1907) organized information about all the known elements in a table that visually organized the similarities between them. Mendeleev placed each element on the table in a certain row and column based on its properties. 18.3 The Periodic Table of Elements

22. The chemical symbol is an abbreviation of the element’s name. The atomic number is the number of protons all atoms of that element have in their nuclei. 18.3 The Periodic Table of Elements

23. The mass number of an element is the total number of protons and neutrons in the nucleus. The atomic mass is the average mass of all the known isotopes of the element. 18.3 The Periodic Table of Elements

24. The symbols for some elements don’t always obviously match their names. 18.3 The Periodic Table of Elements

25. Key Question: What does atomic structure have to do with the periodic table? 18.3 The Periodic Table of Elements *Read text section 18.3 BEFORE Investigation 18.3