Arnoldi Chemistry Atomic Theory One Ch 4 Reading (sections 1 – 3) Ch 5 Reading (sections 1 and 3) 4.1 Defining the Atom 1. Important Definitions atom 2. Why is it so hard to study atoms? (Look at the Question on page 92) 3. How did Democritus describe the atom? 4. What is one of the weaknesses of Democritus’ theory? 5. Dalton had several main ideas in his atomic theory: All matter is (elements are) made of All atoms of the same element are are completely different. _____________ which are indivisible. __________. All atoms of ___________ elements To make compounds, atoms of different elements combine number ratios. 6. What made Dalton’s theory superior to Democritus’ theory? 7. What tool helps us to see and manipulate atoms? ___________ in simple, whole 4.2 Structure of the Nuclear Atom 1. Atoms are not indivisible. They are broken down into several smaller particles that are collectively called _____________ particles. 2. Electrons have a ___________ charge. They were discovered by _______________ using a cathode ray tube. A cathode ray is a stream of electrons produced at the negative electrode (_____________) of a tube containing gas at low pressure. 3. How did Thomson figure out that the cathode ray had a negative charge? 4. Read the Build Connections box on page 96. do you have a CRT TV or computer monitor in your house? 5. Positively charged subatomic particles are called ____________ and were discovered by Goldstein. 6. James Chadwick discovered the neutral subatomic particle, which is called a ____________. 7. Describe or diagram Rutherford’s experiment. What were the conclusions from this experiment? 8. Today, how would you describe the structure of the atom? (look at the Key Question on page 99). 4.3 Distinguishing Among Atoms 1. Definition a. Atomic Number b. Mass Number c. Isotopes d. Atomic Mass 2. What one factor distinguishes one element from another? 3. What is true for all neutral atoms? the number of protons 4. How can you determine the number of neutrons in an atom? 5. Answer practice problem # 21 (a and b) on page 103 here: a. b. 6. How many protons, electrons and neutrons in Carbon – 13? _____ the number of electrons 7. Which subatomic particle stays the same in two different isotopes of the same element? 8. Why do isotopes have different mass numbers? 9. Why is it called an ISOtope? (see the Build Vocabulary box on page 104) 10. What is the unit and its abbreviation that we use to measure the mass of an atom? 5.1 Models of the Atom Pages 118 to 119 only 1. Where did Bohr place electrons in his atomic model? 2. Look at the picture of the two ladders on page 119. What is this picture trying to illustrate about the difference in energy between different energy levels?