2/19/16 Do Now On your half sheet of paper, identify the scientist that either discovered a part of the atom or developed a theory related to atomic structure.
Vocabulary Review Atom Cathode Ray Electrons Protons Neutrons Nucleus
How many protons, electrons, and neutrons are in the element Tin (Sn)? By the end of today, you will know how to find the answer
Atomic Structure Protons, Neutrons, and Electrons SLO 2/19/16 Students will be able to interpret how elements are different from each other and how atomic mass and atomic numbers are determined.
4.3 Distinguishing Among Atoms Just as apples come in different varieties, a chemical element can come in different varieties called isotopes.
Protons Protons- determine the identity of an atom Elements are different because they each have different #s of protons The atomic number of an element is the number of protons in the nucleus of an atom of that element You can find this number by looking at your periodic table In a neutral atom, the number of protons is equal to the number of electrons
Atomic Number
Practice Finding # of protons and electrons
Finding the number of Neutrons The total number of protons and neutrons in an atom is called the mass number. The number of neutrons in an atom is the difference between the mass number and atomic number. How do I find the mass number? If given, add the protons and neutrons together If not, round the mass from the periodic table to the nearest whole number. This will provide the mass number of the most common isotope.
Finding Protons, Neutrons, Electrons You may be given only the name of an element and be expected to look it up on the periodic table. You may be given a symbol with mass numbers and atomic numbers beside it.
Writing and Interpreting Chemical Symbols
Mass of an atom Nucleus- contains most of the mass of an atom Protons & Neutrons contain most of an atom s mass Mass of proton = mass of neutron = 1amu Electrons- 1/2000 th of the mass of a proton
Atomic structure Grams are not used to measure mass of atoms because atoms are too small Amu is used instead Amu = atomic mass unit Amu 1/12 th the mass of a carbon-12 atom, which contains 6 protons and 6 neutrons
Isotopes Isotopes are atoms that have the same number of protons but different numbers of neutrons. Because isotopes of an element have different numbers of neutrons, they also have different mass numbers.
4.3 Isotopes Despite these differences, isotopes are chemically alike because they have identical numbers of protons and electrons.
Isotopes To indicate the identity of an isotope, write the element name mass # Carbon-12 Carbon-14 Isotopes can also be indicated using the method we saw earlier
Independent Practice Work on the Protons, Neutrons, and Electrons of Elements worksheet. This will count as a classwork grade when finished.
Element Symbol Protons Electrons Neutrons Hydrogen H 1 1 0 Lithium Sodium Potassium Rubidium Cesium Francium Beryllium Magnesium Calcium Strontium Barium Radium
For the Quiz Define and indicate location of: Proton Neutron Electron Explain: Dalton s Theory Thomson s Theory Rutherford s Theory
Dalton 1) All elements are composed of tiny indivisible particles called atoms. 2) Atoms of the same element are identical. The atoms of any one element are different from those of any other element. 3) Atoms of different elements can chemically combine in simple whole-number ratios to form compounds. 4) Atoms of one element are never changed into atoms of another element in a chemical reaction. Thomson Plum Pudding Model Atoms have positive and negative charges Discovered the Electron Rutherford Gold Foil Experiment Alpha particles projected toward gold foil Atoms mostly empty space Nucleus- region of high mass and positive charge
Plum Pudding Model
Finish the chart: Element Symbol Atomic Mass Number Number Hydrogen H 1 1 Protons Electrons Neutrons Lithium 3 3 3 4 Na 11 23 (22.99) 11 12 Potassium K 39 (39.09) 19 19 Rubidium 37 37 38 Cesium Cs 133 (132.91) 55 78 Fr 87 87 87 136 Beryllium Be 9 (9.01) 4 Magnesium 12 24 (24.30) 12 12
Homework Reading Assignment: Section 4.3 Written Assignment: Complete the Atomic Identifiers Worksheet Quiz Wed (11/20/13) on Atomic Theory and Structure. Chapter 4, Sections 1 & 2 Complete Pre-Lab for Mass of Candium Lab found on page 120 of the textbook. Lab will be on Friday, November 22nd.
2/22/16 Do Now
Homework Check!
Vocabulary Review Mass number Atom Isotope Cathode Ray Electrons Atomic number Protons Neutrons Nucleus
Quiz Time! You have 35 minutes to complete the quiz.
11/14/14 SLO Students will be able to calculate the average atomic mass of elements and isotopes.
Homework! Complete Pre-Lab for Mass of Candium Lab found on page 120 of the textbook. Lab will be on Friday, November 22nd.
Calculating the Average atomic mass of an element Average atomic mass- a weighted average of the masses of the isotopes of an element Average atomic mass = (% x mass) + (% x mass) + (% x mass).
Example of average atomic mass for carbon mass number 13 exact weight percent abundance 12 12.0000 amu 98.90 13 13.003355 amu 1.10 (12.0000amu) (0.9890) + (13.003355amu) (0.0110) = 12.011 amu
Check your answers C has an average atomic mass of 12.011 amu. This is closer to 12 than to 13, which means most isotopes must be carbon-12. This matches our known data, which say that 98.90% of carbon atoms are C-12.
Isotopes and Weighted Averages Ways to write isotopes: Carbon-14 14 C 14 6 C
Isotopes and Weighted Averages Nitrogen has two isotopes; Nitrogen-14 with a 99.634% abundance and Nitrogen- 15 with a 0.366% abundance. Calculate the Average Atomic Mass. Step 1: Write out the mass number and % abundance as a multiplication problem with a decimal 14 N = 99.634% (14)x(.99634) = 15 N = 0.366% (15)x(.00366) =
Isotopes and Weighted Averages Nitrogen has two isotopes; Nitrogen-14 with a 99.634% abundance and Nitrogen- 15 with a 0.366% abundance. Calculate the Average Atomic Mass. Step 2: Do your math and multiply. 14 N = 99.634% (14)x(.99634) = 13.94876 15 N = 0.366% (15)x(.00366) = 0.0549
Isotopes and Weighted Averages Nitrogen has two isotopes; Nitrogen-14 with a 99.634% abundance and Nitrogen- 15 with a 0.366% abundance. Calculate the Average Atomic Mass. Step 3: Add the products together to get the average atomic mass of the element. 14 N = 99.534% (14)x(.99534) = 13.94876 15 N = 0.366% (15)x(.00366) = 0.0549 + 14.00366
Isotopes and Weighted Averages Try these: Find the average atomic mass of Potassium given the isotopes and relative abundances: Potassium -39 (93.26%) Potassium -40 (0.012%) Potassium -41 (6.73%)
Isotopes and Weighted Averages Try these: Find the average atomic mass of Molybdenum given the isotopes and relative abundances: 92 Mo 14.84% 94 Mo 9.25% 95 Mo 15.92% 96 Mo 16.68% 97 Mo 9.55% 98 Mo 24.13% 100 Mo 9.63%
Throughout this section, we ve been using the periodic table A periodic table is an arrangement of elements in which the elements are separated into groups based on a set of repeating properties. A periodic table allows you to easily compare the properties of one element (or a group of elements) to another element (or group of elements).
Periodic Table Each horizontal row of the periodic table is called a period. Within a given period, the properties of the elements vary as you move across it from element to element. This occurs because they have a different number of outer shell (or valence) electrons
4.3 The Periodic Table A Preview A Period
Periodic Table Each vertical column of the periodic table is called a group, or family. Elements within a group have similar chemical and physical properties. This occurs because they have the same number of valence (or outer shell) electrons
4.3 The Periodic Table A Preview A Group or Family
Homework! Complete Pre-Lab for Mass of Candium Lab found on page 120 of the textbook. Lab will be on Friday, November 22nd.