DO NOW How many electrons, protons, and neutrons does Uranium have? LecturePLUS Timberlake

The Atom Atomic Number and Mass Number Isotopes LecturePLUS Timberlake

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 LecturePLUS Timberlake

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

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

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

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 Timberlake

Periodic Table LecturePLUS Timberlake 11 Na

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

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

Learning Check AT 1 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 Timberlake

Solution AT 1 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 Timberlake

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

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

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 Timberlake

More Atomic Symbols O P Zn p + 15 p + 30 p + 8 n16 n35 n 8 e - 15 e - 30 e - LecturePLUS Timberlake

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 Timberlake

Learning Check AT 2 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 Timberlake

Solution AT 2 12 C 13 C 14 C #P __6___ _ 6___ ___6___ #N __6___ _ _7___ ___8___ #E __6___ _ 6___ ___6___ LecturePLUS Timberlake

Learning Check AT 3 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 Timberlake

Solution AT 3 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 Timberlake

Learning Check AT 4 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 Timberlake

Solution AT 4 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 Timberlake

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) Ca3) Se D.Another isotope of this element is 1) 34 X 2) 34 X 3) 36 X LecturePLUS Timberlake

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 Timberlake

Do Now Complete Do Now Worksheet and please include the question below on to your worksheet. What is an Isotope? LecturePLUS Timberlake

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 Timberlake

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 LecturePLUS Timberlake Na 22.99

Learning Check 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 Timberlake

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 Timberlake

Calculating Atomic Mass Percent(%) abundance of isotopes Mass of each isotope of that element Weighted average = mass isotope 1 (%) + mass isotope 2 (%) + … LecturePLUS Timberlake

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 LecturePLUS Timberlake Mg 24.3

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 Timberlake

AT 7 IsotopeMass%Convert Percentage Multiply Mass with % Mass by % Gallium %60.2/100= x.602= 41.5 amu Gallium %39.8/100= x.398= 28.2 amu LecturePLUS Timberlake Now we add the masses of both isotopes to get the Average Atomic Mass amu amu = 69.7 amu Average Atomic Mass of Ga = 69.7 amu

Let’s Practice Look at Question 1 on your practice handout. LecturePLUS Timberlake

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 Timberlake

Assign X and Y values: X = 10 B =10 amu Y = 11 B =11 amu Determine Y in terms of X X + Y = 100% or 1.0 In this case we will use 1.0 to represent 100% X + Y = 1.0 Subtract X in order to solve for Y Y = X LecturePLUS Timberlake

Now we will solve for X: X + Y = 10.8  Average atomic mass of Boron Insert the mass for X and Y (10)X + (11) (1.0 – X) = X + 11 – 11X = X - 11X = 10.8 – 11 -1X = -.20  Multiply by -1 to get rid of the negative X =.20 Multiply by 100% to get percentage X =.20 x 100% = 20% LecturePLUS Timberlake

So if X = 20% Then Y = 80% How: X + Y = 100% Y = 100% - X Y= 100% - 20% Y = 80% So Boron–10 = 20% and Boron-11= 80% LecturePLUS Timberlake

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) LecturePLUS Timberlake

Solution AT8 Copper–63= 70% Copper–65= 30% LecturePLUS Timberlake