Chemistry Chapter 3

1. Chemistry Chapter3 Atoms: The Building Blocks of Matter

2. Atom who? • Atom • The ________ particle of an element that retains the _____________ of that element Law of Conservation of Mass Mass is neither _________ __________ during chemical or physical reactions. Total mass of __________ = Total mass of __________ Antoine Lavoisier

3. Dalton’s Atomic Theory (1808) • All matter is composed of extremely small particles called ________. • Atoms of a given element are ________ in size, mass, and other properties; atoms of __________ elements differ in size, mass, and other properties. John Dalton • Atoms ________ be subdivided, created, or destroyed. • Atoms of different elements combine in simple ________________ to form chemical compounds. • In _____________, atoms are combined, separated, or rearranged.

4. Modern Atomic Theory Changes have been made to Dalton’s theory.. Dalton said: Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties Modern theory states: Atoms of an element have a characteristic ___________ which is unique to that element. Dalton said: Atoms cannot be subdivided, created, or destroyed Modern theory states: Atoms cannot be subdivided, created, or destroyed in __________________. However, these changes CAN occur in nuclear reactions!

5. Discovery of the Electron In 1897, J.J. Thomson used a cathode ray tube to deduce the presence of a _________ charged particle. Cathode ray tubes pass __________ through a gas that is contained at a very low pressure.

6. Mass of the Electron 1909 – Robert Millikan determines the mass of the electron. The oil drop apparatus Mass of the electron is _____________and the charge is _____________

7. Conclusions from the Study of the Electron • Electrons are ___________. • Cathode rays have _________ properties regardless of the element used to produce them. All elements must contain _________ charged electrons. • Atoms are ________, so there must be ________ particles in the atom to balance the ________ charge of the electrons • Electrons have so ______ mass that atoms must contain other particles that account for most of the mass

8. Rutherford’s Gold Foil Experiment • Alpha particles are ________ charged • Particles were fired at a thin sheet of gold foil • Particle hits on the detecting screen (film) are recorded

9. Rutherford’s Findings • _____ of the particles passed right through • A _____ particles were deflected • VERY ______ were greatly deflected Conclusions: • The nucleus is ______ • The nucleus is _____ • The nucleus is ________ charged

10. The Structure of the Atom • Atoms consist of two regions • _________ • Very small region in the center. • Contains protons & neutrons (nucleons). • __________ • Mainly empty space. • Very large compared to the nucleus. • Contains electrons. • Subatomic particles

11. Atomic Number Atomic number (Z) of an element is the number of ________ in the nucleus of each atom of that element. Identifies the atom. Mass Number Mass number is the number of _______ and ________ in the nucleus of an isotope. Mass # = p+ + n0

12. Isotopes Elements occur in nature as mixtures ofisotopes. Isotopes are atoms of the __________ that differ in the number of _______

13. Isotopes…Again (must be on the test) Isotopes are atoms of the same element having different masses due to varying numbers of neutrons.

14. Atomic Masses Atomic mass is the ________ of all the naturally isotopes of that element. On Periodic Table Carbon =

15. Writing Nuclear Symbols He 3 Mass # (____________) Atomic Symbol Atomic # (_______) 2 How many protons, electrons, and neutrons?

16. Writing Isotopes Using Hyphen Notation Uranium-235, Helium-3, or Carbon-14 How many proton, electrons, neutrons? Name of atom Mass #

17. Isotope problems Convert these hyphen notation to nuclear symbols. Uranium-235, Helium-3, or Carbon-14

18. The Nucleus • Contains nucleons • ________________ • _____________ • Short-range proton-neutron, proton-proton, and neutron-neutron forces hold the nuclear particles together.

19. NuclearStability Decay will occur in such a way as to return a nucleus to the band (line) of stability. Kinetic Stability describes the probability that a nucleus will decompose (radioactive decay)

20. Number of Stable Nuclides Related to Numbers of Protons and Neurons

21. Types of Radioactive Decay • alpha production (a): helium nucleus _____ • beta production (b): _____

22. Types of Radioactive Decay • gamma ray production (g): • positron production : • electron capture: (inner-orbital electron is captured by the nucleus) 0 e 1

23. Types of Radiation

24. The Decay of a 10.0-g Sample of Strontium-90 Over Time

25. QUESTIONS

26. QUESTIONS