Atom In-class review
1. What is an atom?
2. What are the three subatomic particles?
3. What's the mass of a proton?
4. What's the charge of a proton?
5. What's the mass of a neutron?
6. What's the charge of a neutron?
7. What's the mass of an electron?
8. What's the charge of an electron?
9. What is an element's atomic number?
10. What is a mass number?
11. What is an atomic mass?
12. If given the mass number and atomic numbers, how do you determine the number of protons?
13. If given the mass number and atomic numbers, how do you determine the number of neutrons?
14. If an atom has no charge, what can you tell me about its subatomic particles?
15. If an atom has a negative charge, what can you tell me about its subatomic particles?
16. What is an ion?
17. What is an isotope?
18. What is the upper number on our periodic tables?
19. What is the lower number (with decimals) on our periodic table?
20. Why isn't the atomic mass on the periodic table a whole number?
21. Which law: compounds always have the same composition by mass?
22. What do all isotopes of carbon have in common?
23. Who first proposed that matter is made up of atoms?
24. Which law: the mass of the reactants in a reaction is equal to the mass of the products.
25. How does Dalton's atomic theory differ from our modern concept?
26. What are some ways of indicating a particular isotope?
27. Where are protons found?
28. Where are neutrons found?
29. Where are electrons found?
30. How many valence electrons would an atom with atomic number of 12 have?
31. What do the dots in a Lewis dot diagram indicate?
Laws leading to Dalton's Atomic Theory Name ______
Period _____ Date ______
1. Lavosier noticed when reactions were conducted in closed containers, there was never any change in mass.
In the reaction 2Mg + O2 ® 2MgO, two units of magnesium (a silvery metal) react with 1 unit of oxygen (a clear gas) to yield 2 units of magnesium oxide (a white powder).
48.6 grams of magnesium (Mg) will react with 32.0 grams of oxygen (O2), to yield 80.6 grams of magnesium oxide (MgO). There were 80.6 grams of reactants (Mg and O2) and 80.6 grams of product (MgO). So the mass of the stuff you start with (the reactants) is always the same as the mass of the stuff you end up with (the products).
Thus, the law of conservation of mass, which states matter is neither created nor destroyed in chemical reactions.
2. Proust noticed that proportion of the masses of any given compound is always the same.
If you have 80.6 grams of MgO, 6/10's of it's mass is magnesium (48.6 g) and 4/10's of its mass is oxygen (32.0 g). If you had 100 grams of MgO, 60 grams (6/10) would be magnesium (60 g) and 40 grams (4/10) would be oxygen (40 g). The ratio of the masses never varies.
Thus the law of definite proportions, which states that the mass ratio of the components of a given substance is always the same.
3. Dalton noticed that when more than one substance is made from the same elements, the ratio of the component masses varies by small whole number multiples. This implies that each component is made of discrete particles with a certain mass. We now call these particles atoms.
The mass of one unit of water, H2O, is 18.0 g. (2 g hydrogen and 16 g oxygen)
The mass of one unit of hydrogen peroxide, H2O2, is 34 g (2 g hydrogen and 32 g oxygen).
H mass in H2O H mass in H2O2 mass ratio of H of the two substances
2 g 2 g 1:1
O mass in H2O O mass in H2O2 mass ratio of O of the two substances
16 g 32 g 1:2 (the masses vary by a small whole number factor: 2)
Thus the law of multiple proportions, which states that when different substances are made of the same elements, their mass ratios always differ by small, whole number multiples.
3. Spectroscopy Lab: Electrons in Atoms Name ______
Period _____ Date ______
Introduction
An element's atoms have a unique arrangement of electrons. Because of this, when energy (like heat or electricity) is applied to them, the electrons will absorb specific quantities of this energy and undergo a brief "quantum leap" to a higher energy level, then return to their more stable original "ground state." As the electrons return to this ground state, the atoms emit the energy they had absorbed as discrete colors of light. Each element emits a characteristic pattern of light which correlates with its unique electron structure. This characteristic pattern (called emission spectrum) of emitted light can be used to identify elements. Today you will examine emission spectra of pure elemental gases excited by electricity. Then you will use your collected data to identify three unknowns.
Procedure
1. Obtain a spectroscope.
2. Go to each of the stations with gas discharge tubes.
3. Hold the spectroscope so the lines produced are vertical.
4. Look at the spectrum that is produced on the left side.
5. Draw what you see with colored pencils.
Helium (He) ______
Mercury (Hg) ______
Krypton (Kr) ______
Hydrogen (H) ______
Neon (Ne) ______
Other (______) ______
6. Once you have the spectra of the "knowns" illustrated, draw the spectra of the "unknowns" (X, Y, and Z). Compare these spectra with those above to identify the unknown elements.
X ______Identity:
Y ______Identity:
Z ______Identity:
Questions
1. What equipment did you use to observe each element's emission spectrum?
2. Why can emission spectra be used to identify elements?
Atoms (Chapter 2) Reading Guide Name ______
Period _____ Date ______
1. On page 52, early ideas about matter are discussed. What were the four fundamental elements that ancient Greek philosophers believed formed all matter?
2. Unlike modern scientists, what did the Greek philosophers NOT do?
3. Approximately how many years ago (the text gives a range) did Democritus propose the existence of tiny particles called atoms?
4. What law did Lavoisier establish when he stated that the mass of the products of a reaction always equals the mass of the initial reactants?
5. Pages 53-54. What does the law of definite proportions state?
6. List the main points of Dalton's atomic theory?
7. The section on page 58 about Antoine Lavoisier is really interesting. Because he couldn't make a living as a chemist, how did he make money?
8. What important component of air did Lavoisier name?
9. What happened to Lavoisier during the Reign of Terror that followed the French Revolution? (Remind Mr. Wieland to tell you the REST OF THE STORY.)
10. Fill in the blanks from the paragraph at the top of page 62. "In other words, atoms ______, referred to as ______.
11. From the section on protons and neutrons, compare the charge on and electron and on a proton.
12. Compare the relative mass of a proton and an electron.
13. At the bottom of page 62, a particle with the same mass as a proton, but no electrical charge, is described. What is this particle called?
14. The nuclear model of the atom is described on page 65. Rutherford bombarded a super-thin sheet of gold foil with positively charged alpha particles. What did Rutherford's team conclude because most of the particles passed through the foil?
15. Because so few particles were deflected, what did they propose?
16. Page 66. Define atomic number and mass number.
17. On page 77, the electron cloud model is discussed. What is an electron cloud?
18. On page 78, energy levels are described. How many electrons can the first energy level hold (the one closest to the nucleus)?
19. How many electrons can the second energy level hold?
20. How many electrons can the third energy level hold?
21. What are the electrons in the outermost energy level called? (This is important to know.)
22. We care about valence electrons because these are the ones that do all the work. Copy the last sentence of the paragraph at the top of page 79.
23. What does a Lewis dot diagram illustrate?
Atomic Components Worksheet Name ______
Period _____ Date ______
Complete the following table. The first three are done as examples.
§ Atomic number is given on the periodic table and equals the number of protons.
§ In a neutral atom, the number of protons equals the number of electrons
§ In a negative ion (a charged atom), the number of electrons exceeds the number of protons. In a positive ion, the number of electrons is less than the number of protons
§ Mass number is the number of particles with mass (protons + neutrons). The number of neutrons must be calculated by subtracting the atomic number from the mass number.
§ If the mass number is not provided, round off the atomic mass given on the periodic table.
§ If a complete symbol is provided, the subscript before the element symbol is the atomic number and the superscript before the element symbol is the mass number. The mass number is also sometimes provided after the element symbol (example C-14).
§ Charges are indicated as superscripts after the element symbol.
Atom/Ion / Atomic No. / Protons / Electrons / Atomic mass / Mass number / NeutronsMg / 12 / 12 / 12 / 24.305 amu / 24 / 12
O-2 / 8 / 8 / 10 / 15.9994 amu / 16 / 8
C-14 / 6 / 6 / 6 / 12.011 amu / 14 / 8
Cl
Cl-1
N
Pb-205
Pb-208
Al
Al+3
Na
Na+1
P
Ca+2
Si
S
K+1
Fe+2
Fe+3
Test: The Atom: Chapter 2 A Please do not write on this test.
Choose the answer that best answers the question or completes the statement.
1) The scientific statement that says that compounds always have exactly the same composition by mass is the _____.
a) atomic theory
b) percentage error
c) law of conservation of matter
d) law of definite proportion
2) The only subatomic particle that does not carry an electric charge is the _____.
a) proton
b) neutron
c) electron
d) nucleus
3) The atomic number of an element whose atoms have 9 protons and 10 neutrons is _____.
a) 9
b) 19
c) 10
d) 18
4) The mass number of an element whose atoms have 12 protons and 13 neutrons is _____.
a) 12
b) 13
c) 25
d) 12.5
5) One isotope of carbon has 6 protons and 6 neutrons. The number of protons and neutrons of a second isotope of carbon would be _____.
a) 7 and 6
b) 6 and 7
c) 7 and 7
d) 6 and 6
6) _____ first proposed that matter is made up of atoms, the smallest particles of matter.
a) Democritus
b) Lavoisier
c) Proust
d) Dalton
7) According to the law of conservation of matter, if 4.0 g of hydrogen react with chlorine to produce 146 g of hydrogen chloride, how many grams of chlorine reacted?
a) 4.0 g
b) 142 g
c) 146 g
d) 150 g
8) Which of the following statements is not a main point of Dalton's atomic theory?
a) All matter is made up of atoms.
b) Atoms are made up of smaller particles
c) Atoms are indivisible.
d) All atoms of one element are exactly alike, but they are different from atoms of other elements.
9) What is a good comparison of the charge of an electron and the charge of a proton?
a) They are equal, but opposite.
b) The charge of the electron is larger.
c) They are the same.
d) The charge of the proton is larger.
10) Iodine-131 and iodine-127 are examples of _____.
a) nuclei
b) isomers
c) isotopes
d) neutrons
11) Which of the following are definitely atoms of the same element?
a) 3 protons, 3 neutrons and 3 protons, 4 neutrons
b) 3 protons, 3 neutrons and 4 protons, 4 neutrons
c) 4 protons, 4 neutrons and 3 protons, 4 neutrons
d) 3 protons, 4 neutrons and 4 protons, 3 neutrons
12) The _____ is where the electron is most likely to be found.
a) energy level
b) electron orbit
c) electron cloud
d) orbit
13) The atomic number of chlorine is 17. How many valence electrons does an atom of chlorine have?
a) 2
b) 7
c) 8
d) 17
14) In a Lewis dot diagram, the dots represent _____ in the atom.
a) all the electrons
b) the valence electrons
c) the protons
d) the neutrons
Use the square from the periodic table shown to match the best answer.
15) Atomic number of chromium
16) Symbol
17) Name of element