Study Guide – Atomic Theory



Study Guide – Atomic Theory

1. Describe the basic idea of the Atomic Theory. Atoms are made of tiny charged particles with a positive nucleus comprised of protons and neutrons surrounded by negatively charged electrons. Atoms are neutrally charged due to the equal number of – particles to + particles

2. Describe Rutherford’s experiment and his two discoveries. Gold foil experiment where he shot alpha particles at gold foil, when he discovered that atoms have a dense, positively charged nucleus. He is also responsible for the discovery of alpha and beta particles.

3. List the three subatomic particles, their symbols, their charges, their relative masses, and their location in the atom. (You can make a chart if it’s easier.) protons (+) located in the nucleus (mass of 1amu), neutrons (0) located in the nucleus (mass of 1 amu), electrons (-) located outside the nucleus in orbitals or energy levels (mass of 1/1840 or approx 1/2000 amu)

4. What is the Atomic Number and its symbol? Why is it so important? The atomic number is the whole number on the periodic table for each element/atom. It is the number or protons in the atom, for example Helium (He) is atomic number 2 because it has 2 protons in it’s nucleus. The symbol is either a capital letter or a capital letter with a lower case letter that stands for the element, so He is Helium’s symbol.

5. What is the Mass Number and its symbol? The mass number is the number of protons + neutrons in nucleus of an atom. It is also the isotope number. There are two ways to write the mass number. 1. C-14 is carbon with 6 protons and 8 neutrons in it’s nucleus. 2. Is with the mass number written to the top left and the atomic number to the bottom left of the symbol. [pic]

6. When an element is written in the following form: lithium – 5

What does the number represent? The 5 states that the mass number is 5, because lithium has an atomic number of 3 (also the number of protons), this means that there are 2 neutrons. 2n+3p =5

7. For the following atom, tell the (a) mass number, (b) atomic number, (c) # protons, (d) # neutrons, and (e) # electrons.

[pic]

Mass # 15, atomic # 7, # of protons 7, # of neutrons 8, and the number of electrons is 7 + 3 because there is a 3- charge which means the atom gained 3 electrons. So there are 10 electrons

8. What are ions? Ions are charged atoms or atoms that have lost or gained electrons. They will either be (+) cations or (-) anions

9. If an atom gains an electron, what happens to its charge? If it loses an electron, what happens to its charge? If an atom gains an electron it becomes negative (-), if an atom loses and electron it becomes positive (+)

10. What is an isotope? An isotope is an atom with a different number of neutrons than protons in it’s nucleus

11. What is the average atomic mass? Why are the atomic masses on the periodic table written as numbers with long decimals? The average atomic mass is the number that is on the bottom of each square in the periodic table, it is calculated by taking the percent abundance of each isotope of an element and multiplying it by the mass number of that isotope. The average atomic mass will be close to the mass number of the most abundant isotope of that element.

12. How is the average atomic mass different from the mass number? The atomic number is the average of all isotopes of an element. The mass number is the total number of protons + neutrons for a single atom of an element.

13. How do you calculate the average atomic mass from the relative abundance? % abundance multiplied by the mass number for each of the isotopes of that element added together.

14. Describe Bohr’s ideas about electrons in their orbits. electrons travel in defined circular orbits around the nucleus.

15. What are energy levels? Energy levels inside an atom are the specific energies that electrons can have when occupying specific orbitals. Electrons can be excited to higher energy levels by absorbing energy from the surroundings. Light is emitted when an electron relaxes from a high energy state to a lower one (rings called electron clouds)

16. What is the emission spectrum? Describe when energy is released.The emissions spectrum shows the amount of energy released or absorbed when an electron moves from one ground state (energy level to another energy level). The emissions spectrum also identifies what times of radiation and visible color of light are released when the electron moves to another energy level.

17. What is a quantum? A quantum is a measure of energy that is proportional in magnitude to the frequency of radiation it represents  

18. What are ground states and excited states? The ground state is the lowest energy level of an atom that is full, the excited state is the highest energy level of an atom that houses the valence electrons (outer most electrons)

19. How are frequency and energy related? How are frequency and wavelength related? As frequency increases, energy also increases. As energy increases, frequency also increases. As frequency and energy increase, wavelength decreases. As wavelength increases, frequency and energy decrease. SO….wavelength is inversely related to frequency and energy. Frequency and energy are directly related.

20. What type of radiation has the highest energy? Highest frequency? Shortest wavelength? Gamm radiation has the highest energy and frequency, while having the shortest wavelength.

21. Describe the model of the atom as we know it today. Who is responsible for it? Explain WHY there are clouds, instead of circular rings today. Today’s atomic model, based on Niels Bohr’s model, is comprised of a (+) nucleus with protons and neutrons in it, with (-)electrons orbiting the nucleus in energy levels called electron clouds. They are called electron clouds due to how difficult it is to find the electrons. They are located in the densest part of the cloud.

22. Does an electron act like a wave, a particle, or both? Both, it is a particle that acts and moves like a wave.

23. Draw the 4 models of the atom as it progressed .know the 4 models

24. What do “energy levels” tell you? How many electrons can be in an atom. Each energy level has a specific number of sublevels, that each have a specific number of electrons it can house.

25. What do “sublevels” tell you? List the 4 sublevels. sublevels tell you where an atom is located in an energy level and how many electrons it can hold. For example energy level 1 has only the S sublevel which can house 2 electrons, energy level 2 has only the S and P sublevel. The P sublevel can house 6 electrons.

26. What do “orbitals” tell you? How many orbitals does each sublevel have? How many electrons can fit in a single orbital? An orbital is an energy level with it’s sublevels. If we use electron notation of orbital notation, we can determine how many sublevels and electrons are located in the orbital. For example if I have Carbon which is element number 6, it is in the P sublevel of the 2nd energy level : 1S2 2S2 2P4 Carbon has 2 energy levels, 2 sublevels and 6 electrons in it’s outermost energy level 2. Orbital notation is represented by arrows, 2 per box: 1 box in S, 3 boxes in P, 5 boxes in D, and 7 boxes in F

27. If 2 electrons are in the same orbital, what should they have? Opposite spins, (one goes up and one goes down. Remember all boxes in an orbital must be half full before being filled. For example the P sublevel will have 3 boxes that fill as follows. Up, up, up, down, down, down.

28. How many total electrons can fit in the 3rd energy level? (Hint: Look at the chart you made in your notes!!) The third energy level ends with 3S2, 3P6, 3D10

29. Write the electron configurations for each element. (You can abbreviate.) (example 1S2 2S2 2P4 )

a) P b) Mo c) Pb

30. Write the orbital notation for each element. (You can abbreviate.) (remember boxes with up and down arrows)

a) Br b) Te c) V

31. What determines the chemical and physical properties of an element? The number of valence or outermost electrons

32. What are valence electrons?The outermost electrons in an atom. These are the electrons that will bond with other atoms to form molecules and compounds

33. How many valence electrons does each atom have?

a) Cl (column 7A so 7) b) K (Column 1A so 1) c) Al (Column 3A or 13 so 3)

Answers:

7) mass # = 15

atomic # = 7

protons = 7

neutrons = 8

electrons = 10

20) Gamma rays for all 3 questions

29) P: [Ne] 3s23p3

Mo: [Kr] 5s24d4

Pb: [Xe] 6s24f145d106p2

30) Br: [Ar] 4s23d104p5

Te: [Kr] 5s24d105p4

V: [Ar] 4s23d3

33) Cl: 7

K: 1

Al: 3

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