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PreAP Chapter 3 Notes ____________________ was the early Greek philosopher who is credited with the concept of the atom (atomos) – which means ____________________ ________________________________________ states that the elements in a specific compound always contain the same proportions by mass ________________________________________ states that if two or more different compounds are composed of the same two elements, then the ratio of the masses of the second element combined with a certain mass of the first element is always a ratio of small whole numbers ____________________ is an English school teacher who proposed the law of conservation of mass, the law of definite proportions, and the law of multiple proportions. He is also known as the ____________________________________________________________ Dalton’s atomic theory 1. All matter is composed of very small particles called ____________________ 2. Atoms of a given element are identical in ____________________, ____________________, and other properties; atoms of different elements differ in these properties. 3. Atoms cannot be ____________________, ____________________, or ____________________ 4. Atoms of ____________________ elements combine in simple ____________________ ratios to form chemical compounds. 5. In chemical reactions, atoms are ____________________, ____________________, or ____________________ Two aspects of Dalton’s atomic theory proven to be incorrect: a. We now know atoms are ____________________ b. Atoms of the same element can have different ____________________ ____________________ - smallest particle of an element that retains the ____________________ of that element. Two regions of an atom 1. ____________________ --small region near the center of the atom. Composed of two particles—the ____________________ which is ____________________ charged and the ____________________ which is ____________________ charged. 2. ____________________ --composed of ____________________ charged electrons. It is very large in comparison to the nucleus. ____________________ particles—protons, neutrons, electrons. ____________________ tubes—the instrument used in the discovery of the electron. ____________________ is the man credited with the discovery of the electrons in the late _____ ____________________ discovered the mass of the electrons. Knowledge of electrons led to two inferences about atomic structure: 1. Because atoms are electrically ____________________, they must contain ____________________ charge to balance the negative electrons. 2. Because electrons have so little mass, atoms must contain other particles to account for most of their ____________________ Nucleus of the atom—discovered by ________________________________________ Gold foil experiment—actually done by ____________________ and ____________________ Observations: a. Majority of the ____________________ particles penetrated foil ____________________ b. About ____________________ in ____________________ were ____________________ deflected c. About ____________________ in ____________________ were deflected ____________________ Conclusions: 1. ___________________ of the atom and the ____________________ charge are concentrated in small regions called ____________________ 2. Most of the atom is ______________________________. 3. __________________________of charge on the nucleus is__________________ for different atoms. 4. Number of ____________________ outside the nucleus + number of units of ____________________ (to account for the fact that the atom is electrically ____________________ Atoms are electrically neutral because they contain equal numbers of ____________________ and ____________________ Rutherford’s Gold Foil Experiment Summary 1. What kinds of particles are being emitted by the radioactive source and what is their charge? _________________________________________________________________________________________________________________ 2. Toward what are the alpha particles being directed? _________________________________________________________________________________________________________________ 3. What happens when the charged particles strike the surface of the gold foil? _________________________________________________________________________________________________________________ 4. What was the purpose of the fluorescent screen? _________________________________________________________________________________________________________________ 5. What did Rutherford conclude from this gold foil experiment regarding the amount of empty space in the atom? Why was he able to conclude this? _________________________________________________________________________________________________________________ _________________________________________________________________________________________________________________ 6. How does the deflection path of a charged particle that strikes the center of a gold atom differ from the path of a particle that passes only near the center? _________________________________________________________________________________________________________________ 7. Based on this experiment, where is most of the positive charge and mass of an atom found? _________________________________________________________________________________________________________________ 8. What would have been observed in the positive charge of an atom had been thinly spread out throughout the atom? _________________________________________________________________________________________________________________ ________________________________________the short-range proton-neutron, proton-proton, and neutron-neutron forces that hold the nuclear particles together Mass of one____________________= mass of one ____________________= mass of 1837 ____________________ Atomic number number of ____________________in the ____________________of the atom. number of ____________________ ____________________ the element and is equal to the number of ____________________ symbol is Z. ____________________are atoms of the same element that have different masses because they have different numbers of ____________________, but they still have similar chemical ____________________ Mass number approximate ____________________of an atom (____________________) the number of ____________________+ the number of ____________________ ____________________is the general term for any isotope of any element ______________ _____________ ___________ (1 _______) is exactly 1/12 the mass of a carbon-12 atom. ______________ _____________ _____________ is the weight average of the atomic masses of the naturally occurring isotopes of an element. Ave. Atomic mass = (%abundance × mass of isotope 1) + (%abundance × mass of isotope 2) +….. Moles ____________________ (_________) is the amount of a substances that contains as many particles as there are atoms in exactly 12 g of carbon-12. ____________________number - ____________________ - is the number of particles in exactly ____________________mole of a pure substance. Just as one dozen = 12 somethings, one mole = ____________________somethings. The mass of one mole of a pure substance (element or compound) is called the ________________________________________of that substance. The unit is _____________. Examples: How many grams are in 2.0 moles of Carbon? _________________________________________________________________________________________ = ________________ How many moles are in 0.58 g Al? _________________________________________________________________________________________ = ________________ How many moles are equal to 1.20 x 1025 atoms of sodium? (Na) _________________________________________________________________________________________ = ________________ How many atoms are in 0.750 mol of zinc? (Zn) _________________________________________________________________________________________ = ________________ What is the mass in grams of 4.75 x 1024 atoms of silver? (Ag) _________________________________________________________________________________________ = ________________ What mass of Antimony (Sb) contains the same number of atoms as 9.0 g of aluminum? _________________________________________________________________________________________ = ________________