LecturePLUS Timberlake1 Atoms and Elements The Atom Atomic Number and Mass Number Isotopes

LecturePLUS Timberlake2

The Atom An atom is the smallest particle that retains the characteristics of an element

LecturePLUS Timberlake4 Atomic Theory Atoms are building blocks of elements Similar atoms in each element Different from atoms of other elements Two or more different atoms bond in simple ratios to form compounds

The Parts of the Atom Atoms are composed of three subatomic particles: Protons have a positive charge (+) Electrons carry a negative charge (-) Neutrons are electrically neutral.

LecturePLUS Timberlake6 Subatomic Particles ParticleSymbol Charge Relative Mass Electron e Proton p Neutron n0 1

LecturePLUS Timberlake7 Location of Subatomic Particles cm electrons protons neutrons cm nucleus

The Structure of the Atom The protons and neutrons, each with a mass of about 1 amu are found in the tiny, dense nucleus. The electrons are located outside the nucleus.

Models of the Atom 9

LecturePLUS Timberlake10 Atomic Number Counts the number of protons in an atom

LecturePLUS Timberlake11 Atomic Number on the Periodic Table 11 Na Atomic Number Symbol

LecturePLUS Timberlake12 All atoms of an element have the same number of protons 11 Na 11 protons Sodium

LecturePLUS Timberlake13 Periodic Table Represents physical and chemical behavior of elements Arranges elements by increasing atomic number Repeats similar properties in columns known as chemical families or groups

LecturePLUS Timberlake14 Periodic Table Na

LecturePLUS Timberlake15 Learning Check State the number of protons for atoms of each of the following: A. Nitrogen 1) 5 protons 2) 7 protons 3) 14 protons B. Sulfur 1) 32 protons 2) 16 protons 3) 6 protons C. Barium 1) 137 protons 2) 81 protons 3) 56 protons

LecturePLUS Timberlake16 Solution State the number of protons for atoms of each of the following: A. Nitrogen 2) 7 protons B. Sulfur 2) 16 protons C. Barium 3) 56 protons

LecturePLUS Timberlake17 Number of Electrons An atom is neutral The net charge is zero Number of protons = Number of electrons Atomic number = Number of electrons

LecturePLUS Timberlake18 Mass Number Counts the number of protons and neutrons in an atom

LecturePLUS Timberlake19 Atomic Symbols Show the mass number and atomic number Give the symbol of the element mass number 23 Na sodium-23 atomic number 11

LecturePLUS Timberlake20 Subatomic Particles in Some Atoms O P Zn p + 15 p + 30 p + 8 n16 n35 n 8 e - 15 e - 30 e -

LecturePLUS Timberlake21 Isotopes Atoms with the same number of protons, but different numbers of neutrons. Atoms of the same element (same atomic number) with different mass numbers Isotopes of chlorine 35 Cl 37 Cl17 chlorine - 35 chlorine - 37

LecturePLUS Timberlake22 Learning Check Naturally occurring carbon consists of three isotopes, 12 C, 13 C, and 14 C. State the number of protons, neutrons, and electrons in each of these carbon atoms. 12 C 13 C 14 C #p _______ _______ _______ #n _______ _______ _______ #e _______ _______ _______

LecturePLUS Timberlake23 Solution 12 C 13 C 14 C #p #n #e 6 6 6

LecturePLUS Timberlake24 Learning Check An atom of zinc has a mass number of 65. A.Number of protons in the zinc atom 1) 302) 353) 65 B.Number of neutrons in the zinc atom 1) 302) 353) 65 C. What is the mass number of a zinc isotope with 37 neutrons? 1) 372) 653) 67

LecturePLUS Timberlake25 Solution An atom of zinc has a mass number of 65. A.Number of protons in the zinc atom 1) 30 B.Number of neutrons in the zinc atom 2) 35 C. What is the mass number of a zinc isotope with 37 neutrons? 3) 67

LecturePLUS Timberlake26 Learning Check Write the atomic symbols for atoms with the following: A. 8 p +, 8 n, 8 e - ___________ B.17p +, 20n, 17e - ___________ C. 47p +, 60 n, 47 e - ___________

LecturePLUS Timberlake27 Solution 16 O A. 8 p +, 8 n, 8 e - 8 B.17p +, 20n, 17e - 37 Cl 17 C. 47p +, 60 n, 47 e Ag 47

LecturePLUS Timberlake28 Learning Check AT 5 An atom has 14 protons and 20 neutrons. A.Its atomic number is 1) 142) 163) 34 B. Its mass number is 1) 142) 163) 34 C. The element is 1) Si2) Ca 3) Se D.Another isotope of this element is 1) 34 X 2) 34 X 3) 36 X

LecturePLUS Timberlake29 Solution AT 5 An atom has 14 protons and 20 neutrons. A.It has atomic number 1) 14 B. It has a mass number of 3) 34 C. The element is 1) Si D.Another isotope of this element would be 3) 36 X 14

LecturePLUS Timberlake30 Masses of Atoms A scale designed for atoms gives their small atomic masses in atomic mass units (amu) An atom of 12 C was assigned an exact mass of amu Relative masses of all other atoms was determined by comparing each to the mass of 12 C An atom twice as heavy has a mass of amu. An atom half as heavy is 6.00 amu.

LecturePLUS Timberlake31 Atomic Mass on the Periodic Table 11 Na Atomic Number Symbol Atomic Mass

LecturePLUS Timberlake32 Atomic Mass Listed on the periodic table Gives the mass of “average” atom of each element compared to 12 C Average atom based on all the isotopes and their abundance % Atomic mass is not a whole number Na 22.99

LecturePLUS Timberlake33 Atomic Mass Atomic mass is the weighted average mass of all the atomic masses of all the isotopes of that atom.

Weighted Average You have two types of coins: pennies and quarters. The pennies have a mass of 5g. The quarters have a mass of 15g. 57% of the coins are pennies, 43% of the coins are quarters. What is the average mass of your coins? 34

Weighted Average – Atomic Mass You have two isotopes of Boron: 10B and 11B. The 10B has a mass of 10amu. The 11B has a mass of 22 amu. 57% of the atoms are 10B, 43% of the atoms are 11B. What is the average mass of your atoms? 35

LecturePLUS Timberlake36 Example of an Average Atomic Mass Cl-35 is about 75.5 % and Cl-37 about 24.5% of natural chlorine. 35 x 75.5 = x 24.5 =

LecturePLUS Timberlake37 Problem AT6 Using the periodic table, specify the atomic mass of each element (round to the tenths place): A.calcium________ B. aluminum________ C. lead________ D. barium________ E. iron________

LecturePLUS Timberlake38 Solution AT6 Using the periodic table, specify the atomic mass of each element (round to the tenths place): A.calcium_40.1 amu _ B. aluminum_27.0 amu _ C. lead_207.2 amu_ D. barium_137.3 amu_ E. iron_55.8 amu__

LecturePLUS Timberlake39 Calculating Atomic Mass Add : Percent (%) abundance of each isotope Multiplied by the Mass of each isotope of that element Weighted average = mass isotope 1 (%) + mass isotope 2 (%) + …

LecturePLUS Timberlake40 Atomic Mass of Magnesium Isotopes Mass of Isotope Abundance 24 Mg =24.0 amu 78.70% 25 Mg = 25.0 amu 10.13% 26 Mg = 26.0 amu 11.17% Atomic mass (average mass) Mg = 24.3 amu Mg 24.3

LecturePLUS Timberlake41 Learning Check AT7 Gallium is a metallic element found in small lasers used in compact disc players. In a sample of gallium, there is 60.2% of gallium-69 (68.9 amu) atoms and 39.8% of gallium-71 (70.9 amu) atoms. What is the atomic mass of gallium ?

LecturePLUS Timberlake42 Solution AT7 Ga amu x 60.2 = 41.5 amu for 69 Ga 100 Ga-71 (%/100) 70.9 amu x 39.8 = 28.2 amu for 71 Ga 100 Atomic mass Ga = 69.7 amu

LecturePLUS Timberlake43 Finding An Isotopic Mass A sample of boron consists of 10 B (mass 10.0 amu) and 11 B (mass 11.0 amu). If the average atomic mass of B is 10.8 amu, what is the % abundance of each boron isotope?

LecturePLUS Timberlake44 Assign X and Y values: X = % 10 B Y = % 11 B Determine Y in terms of X X + Y = 100 Y = X Solve for X: X (10.0) + (100 - X )(11.0) = Multiply through by X X = 1080

LecturePLUS Timberlake45 Collect X terms 10.0 X X = X = X = 20 % 10 B Y = X % 11 B = % = 80% 11 B

LecturePLUS Timberlake46 Learning Check AT8 Copper has two isotopes 63 Cu (62.9 amu) and 65 Cu (64.9 amu). What is the % abundance of each isotope? (Hint: Check periodic table for atomic mass) 1) 30%2) 70%3) 100%

LecturePLUS Timberlake47 Solution AT8 2) 70% Solution X + Y= 100 Y = X Solve for X: X (62.9) + (100 - X )(64.9) = Multiply through by X X = X = -140 X = 70%