Unit 3: Atoms and Periodic Table Retake Review Packet

Transcription

1 Name Date Block Unit 3: Atoms and Periodic Table Retake Review Packet Completing each section of the retake review packet will fulfill one of the requirements for retaking the unit 3 test. Section 1: Vocabulary Directions: Complete the explanation of these vocabulary terms based on the teachers discretion. Atom Subatomic particles Proton Neutron Electron Nucleus Negative Positive Atomic number Mass number Isotopes Energy levels Electron cloud Period Valence Electron Group/Family Section 2: History of the Atomic Theory Directions: Go to Read through the 10 slides shown on the website and answer the following questions: 1. What did the Greeks (Democritus) contribute to our modern day understanding of what matter is made up of? 2. What particle did J.J. Thomson discover and what did his model of the atom look like (describe in your own words the picture shown on the website)? 3. How did Rutherford s model of the atom change compared to J.J. Thomson s model? Draw an example of Rutherford s model. 4. What was Bohr studying that led to his new model of the atom? Draw a picture of what his model looked like.

2 Section 3: Structure of the atom: All matter (solid, liquid or gaseous) consists of elements, of which there are more than 100. If, in theory, we cut a block of iron into smaller and smaller pieces, we would finally end up with the smallest piece possible that still has all the characteristics of the iron element. That smallest piece is called an iron atom. An atom is very, very small. In fact, the size of an atom compared to the size of an apple, is like the size of an apple compared to the size of the Earth. Most atoms consist of three basic particles: protons (with a positive electrical charge), electrons (with a negative electrical charge), and neutrons (with no electrical charge). Protons and neutrons are bundled together in the center of the atom, called the nucleus. The electrons move around the nucleus, each in its own orbit like the moon around the earth. Each atom of the same element is characterized by a certain number of protons in the nucleus. That number is called the atomic number. Normally, the atom has the same number of electrons in orbit around the nucleus. This atomic number identifies the elements. The list of elements (ranked according to an increasing number of protons) is called the Periodic Table. For example, Helium has 2 protons in its nucleus. Its atomic number is therefore 2. Iron has 26 protons in its nucleus. Its atomic number is therefore 26. Uranium has 92 protons. Its atomic number is therefore 92. Even though the number of protons in the nucleus is the same for all atoms of a particular element, the number of neutrons in the nucleus can differ for different atoms of the same element. Atoms of an element that contain the same number of protons, but different numbers of neutrons, are called isotopes of the element. Isotopes are identified by adding the number of protons and neutrons together -- a number which is referred to as the mass number. 5. Complete the table below for all Neutral Atoms (excluding Ions and Isotopes) Atomic symbol Atomic number Protons Neutrons Electrons Atomic mass Be Bi

3 Isotopes: All the atoms of an element have the same atomic number, but they can have different numbers of neutrons and different mass numbers. Isotopes of an element are atoms that have the same number of protons, but different numbers of neutrons. Examples of isotopes are the three different kinds of carbon atoms where all have 6 protons, but different numbers of neutrons specifically 8, 7 and 6 neutrons respectively. Examples of the carbon isotopes: Carbon-14 = 8 neutrons Carbon-13 = 7 neutrons Carbon-12 = 6 neutrons Naming Isotopes: an isotope name contains the name of the element and the mass of the isotope. Carbon-14 Carbon-13 Carbon-12 Greek "iso" means same and "topos" means place. This fits the idea that isotopes are in the same place in the periodic table, but have different masses. Periodic table entries provide the information shown here. The periodic table does not indicate isotope information. Isotope abundances: The isotopes of an element do not occur with equal frequency. The relative abundance depends on the relative stability of the isotope. The isotopes contribute to the average atomic mass based on their abundance. The result is that the most abundant or common isotope dictates the average mass for the atoms of an element. The atomic masses in the periodic table are weighted averages. This means the tabulated value doesn't match any actual atom, but is closer to the most common isotope.

4 How to Calculate an Average Atomic mass Example #1: Carbon Mass number Percent abundance % % To calculate the average atomic weight, each exact atomic weight is multiplied by its percent abundance (expressed as a decimal). Then, add the results together and round off to an appropriate number of significant figures (hundredths place will be fine for now). This is the solution for carbon: Work (12) (0.9890) + (13) (0.0110) = 12.01amu 6.) Calculate the average atomic mass of magnesium; show your work to the right of each problem, and round your answers to the hundredths place. mass number Percent abundance % % % (show your work here) 7.) Compare and contrast the atomic structure of the carbon-12 and carbon-14 isotopes using a double bubble map. C-12 C - 14

5 Section 4: Valence Electrons The valence electrons are the electrons in the last shell or energy level of an atom. They do show a repeating or periodic pattern. The valence electrons increase in number as you go across a period. Then when you start the new period, the number drops back down to one and starts increasing again. For example, when you go across the table from carbon to nitrogen to oxygen, the number of valence electrons increases from 4 to 5 to 6. As we go from fluorine to neon to sodium, the number of valence electrons increases from 7 to 8 and then drops down to 1 when we start the new period with sodium. Within a group-- starting with carbon and going down to silicon and germanium--the number of valence electrons stays the same. Na 1 C 4 Si 4 Ge 4 N 5 O 6 F 7 Ne 8 A quick way to determine the number of valence electrons for a representative element is to look at which group is it in. Elements in group I have 1 valence electron. Elements in group 2 have 2 valence electrons. Section 5: Periodic Table Properties and Trends Directions: Please access the following websites on the internet and answer the following questions. search for Groups of the Periodic Table by kahnacademy. Go to and search for Periodic Table: Groups and Trends by Mintydiablo. 8.) Define a family. 9.) What is a period? 10.) What period are the following elements in? a. He b. Ge c. Rb d. I 11.) What group are the following elements? a. Sulfur b. Ca c. Iodine d. Fe

6 12.) Give me an atom with the following characteristics. a. Halogen b. Nonmetal c. Alkali metal d. metalloid e. Lanthanide series f. Alkaline Earth metal g. Transition metal h. Nobel gas 13.) How many valence electrons are in the following element? a. F b. Cl c. Br d. I e. O f. S g. Se h. Te 14.) By looking at the valence electrons why are F, Cl, Br and Iodine in the same column of the periodic table? 15.) Create a circle that fills the whole box where the largest atom exists in the periodic table. 16.) Put a dot where the smallest atom is in the periodic table. 17.) Draw an arrow from the circle to the dot. 18.) Write on the line of the arrow. (Atomic size Increases) 19.) Write an arrow showing the trend for increasing Valence Electrons. 20.) Write another arrow showing the trend for increasing Mass Numbers of elements.