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Name: _______________________________________________ Date: _______________ Period: ________ Chapter 4 Notes Development of Atomic Theory 1. Democritus named atoms from the Greek word that means ____________________. 2. During Aristotle’s it was believed that all substances were built from the four elements ________________, air, _____________________ and water. 3. By the 1800s Dalton’s ideas replaced the Greeks, and he proposed that all ________________ is made up of individual _______________ that could not be ____________________. 4. There were four major points to Dalton’s theory a. All elements are composed of ___________________. b. All atoms of the same element have the same _________________, and atoms of different elements have different ____________________. c. Compounds contain atoms of more than one ________________. d. In a particular compound, atoms of different elements __________________________ combine in the same way. 5. Although Dalton’s theory was widely accepted, scientists began experimenting to see if Dalton’s theory was true. Thomson’s experiment provided the ________________ evidence that atoms are made of ______________________ particles. 6. Thomson believed that____________ are neutral, having neither a negative or positive charge and that the charges were ______________________ ____________________ throughout the atom. His model was called the ______________ ___________________ model. 7. Rutherford tested Thomson’s model to see if the charges were scattered. He was surprised when some particles were ________________________. 8. In the Gold Foil experiment, Rutherford shot _________________ particles at a thin sheet of gold foil. He found that as the alpha particles got closer to the center they were more _______________________. 9. Rutherford concluded that the positive charges in the atom are ____________________ at the center called the ___________________________. Subatomic Particles 10. Rutherford found the first two subatomic particles, and proposed a third particle. These particles are _________________________, ________________________ and _____________________. 11. Rutherford concluded that the amount of ____________________ charge varies by element. Each positive charge comes from a _____________________ which is found in the ______________________ of an atom. Each one has a ___________ charge. 12. ______________________, on the other hand, are ____________________ charged and are located __________________ the nucleus. Each one has a _____________ charge. 13. The ______________________ is a neutral subatomic particle located ________ the nucleus. It mass is almost _________________ to the mass of a proton. 14. Electrons have a much ___________________ mass than protons. 15. The charge of electrons and protons are the ______________magnitude but the particles have ____________________ sign. 16. Protons and neutrons are found ___________________ the nucleus and electrons are _______________________. Name: _______________________________________________ Date: _______________ Period: ________ 17. The number of protons in an atom is the ___________________ number. All atoms of the same element have the _____________________ number of protons. Atoms of ________________________ elements have ______________________ numbers of protons. 18. The ___________________ ________________________ of an atom is the sum of the _______________________ and ______________________ in the nucleus of the atom. 19. If you know the atomic number and the mass number of an atom, you can find the number of neutrons by subtracting. Number of neutrons = ______________________ number-_________________ number 20. __________________________ are atoms of elements that have the same numbers of _____________________, but different numbers of _______________________. Isotopes of elements have different _________________________ numbers. Bohr Model 21. Bohr’s model of the atom differed from Rutherford’s in that it focused on the _________________________. 22. In Bohr's model, electrons move with constant speed in __________________orbits around the nucleus. Each electron has a _________________ amount of energy. 23. The possible energies that electrons in an atom can have are called _____________________ _____________________. 24. An electron in an atom can move from one energy level to another when the atom ____________________ or __________________ energy. Modern Atomic Theory 25. An _____________________ cloud is a visual model of the most likely locations for _______________________ in an atom. The cloud is denser at those locations where the _____________________________ of finding an electron is high. 26. The electron cloud represents all the ________________________ in an atom. An orbital is a region of _____________________ around the nucleus where an electron is ________________________ to be found. 27. Each energy level can contain a certain number of orbitals. Each orbital can contain ____________ electrons at most as seen in the table below: Energy Level Number of Orbitals Maximum Number of Electrons 1 2 3 4 28. An ________________________ configuration is the arrangement of electrons in the __________________ of an atom. Name: _______________________________________________ Date: _______________ Period: ________ 29. The most stable electron configuration is the one in which the electrons are in orbitals with the _________________________ possible energies. When all the electrons in an atom have the possible energies, the atom is said to be in its __________________________ state. 30. If an atom _____________________ enough energy, one of its electrons can move to an orbital with a ______________________ energy.