instructions? 1. Dalton wrote which theory? Review Answer the following quest. on the blank sheet of paper. 1. Dalton wrote which theory? 2. List the 3 subatomic particles. 3. Which two subatomic particles make-up the nucleus? 4. A negatively charged particle is called an ___________. 5. Draw a circle on your paper, inside the circle draw the nucleus, e-, p+ and n0 for the atom Carbon. instructions?

6. Most of the mass of an atom is found where? Warm-up Directions: # paper 6-10, write just the answer 6. Most of the mass of an atom is found where? 7. Whose theory states that all atoms of the same element are identical? 8. Which experiment led to the discovery of the nucleus? 9. What is the charge on the nucleus? What cancels out this charge? 10. A cathode ray proved the presence of an _____ & a canal ray showed ___ were present in an atom. What piece of equipment was used?

Distinguishing between atoms & atoms of an element. Atomic Structure and Isotopes Distinguishing between atoms & atoms of an element.

Protons, Neutrons and Electrons I. Subatomic particles The atom contains 3 subatomic particles: Protons, Neutrons and Electrons A. Elements are different from one another due to their number of protons. Atomic # = # of protons 1. The # of protons: Identifies an element Increases left to right across each row How many p+ are in Boron?

B. Atoms are electrically neutral. # of protons = # of electrons 1. The # of electrons: Determines the chemical reactivity of the element How many e- are in Boron? 2. If an atom: Gains or loses electrons it is called an ION! Why would an atom gain or lose e- ? To become stable.

Mass # = Protons + Neutrons C. The mass of an atom is concentrated in the atoms nucleus. Mass # = Protons + Neutrons D. The mass # is: A whole #. Why are electrons NOT included in the calculation for mass #? Electron mass is negligible compared to protons. What is the mass # for C?

How many neutrons are there in an atom of Ag? 61 neutrons E. Calculating the # of neutrons Neutrons = Mass # - Atomic # How many neutrons are there in an atom of Ag? 108 - 47 = 61 neutrons Electron mass is negligible compared to protons.

Element  Ag Cl - 35 How many n0 are in Cu? 64 – 29 = 35 Mass # 108 47 Atomic # How many n0 are in Cu? 64 – 29 = 35 Write the atom, Chlorine, in the form of “symbol of element-mass #”. Electron mass is negligible compared to protons. Cl - 35

Review: Review Atomic # = # of protons # of protons = # of electrons Mass # = Protons + Neutrons Electron mass is negligible compared to protons. Mass # - Atomic # Neutrons = Review

Lecture notes K Be 4 5 4 Ne 10 10 10 19 20 19 Element Protons Neutrons Electrons 9 4   20 10 K Be 4 5 4 Ne 10 10 10 19 20 19

II. Average Atomic mass or amu A. The amu is the sum of protons & neutrons in the nucleus and the relative abundance of isotopes. Average Atomic mass is a decimal #. 11 Atomic Number Na Sodium Because the protons and neutrons are whole numbers but the isotope is the relative abundance in nature a percent or average abundance. The relative atomic mass of an element is the average mass of all the isotopes present compared to 1/12th of the mass of carbon-12 atom (12C = 12.00000 ie the standard). Amu 22.99 The mass # would be 23 g, doesn’t include isotopes.

Important Information: 1. The average atomic mass of an element is usually closest to the isotope with the highest natural abundance. 2. Elements with an average atomic mass close to a whole number exist predominantly in nature as one natural isotope. 3. In nature most elements occur as 2 or more isotopes.

Examples: Which isotope of Cu is more abundant: Cu-63 or Cu-65 (atomic mass of Cu is 63.55 amu)? Boron has 2 isotopes: B-10 and B-11. Which is more abundant, given that the atomic mass of boron is 10.81? Cu-63, B-11, 28- most abundant, 29-2nd, 30-last There are 3 isotopes of Si; they have a mass # of 30, 29, & 28. The atomic mass of Si is 28.086 amu. Which is the most abundant, 2nd abundant and least.

YES III. Isotopes A. What is an isotope? An atom of an element that has a different number of neutrons while the protons and electrons remain the same. B. Are isotopes of an element chemically the same? YES Neutrons only change the mass, e- and p+ stay the same.

C. How do isotopes of the same element differ? 1. different number of neutrons. 2. Only the mass changes! D. Write the formula for the following isotopes of chlorine, Cl-35 & Cl-37. 35 37 Cl Cl 17 17 18 neutrons 20 neutrons Determine the # of neutrons in each isotope of chlorine.

IV. How is the average atomic mass unit defined? A. The unit is based on a reference isotope or standard, carbon-12 isotope, that has a mass of exactly 12 amu. 1. The mass of a single p+ or n0 is ~1 amu. A carbon-12 atom has six protons and six neutrons in its nucleus and its mass is set at 12 amu. The protons and neutrons account for nearly all of its mass. Therefore, the mass of a single proton or neutron is 1/12 of 12 amu, or about 1 amu.

X How is the average atomic mass of an element determined? Formula: % abundance of isotope in decimal form Mass of the isotope X A carbon-12 atom has six protons and six neutrons in its nucleus and its mass is set at 12 amu. The protons and neutrons account for nearly all of its mass. Therefore, the mass of a single proton or neutron is 1/12 of 12 amu, or about 1 amu. The sum of the individual isotope mass contributions will equal the atomic mass.

X X = = X + = Examples: Formula: .754 26 amu Cl – 35 = 35 amu 9.1 amu % abundance of isotope in decimal form Mass of the isotope X Formula: Determine the atomic mass of chlorine given two known isotopes, Cl-35 & Cl-37. The relative abundances are 75.4% & 24.6%. X .754 = 26 amu Cl – 35 = 35 amu Do the example on worksheet A = 9.1 amu Cl – 37 = X 37 amu .246 + = 26 amu 9.1 amu 35.1 amu 35 amu

Instructions Convert 3.94 inches/hr to meters/sec Convert 54 nL to uL Take out your calculator & laminated periodic table Take out your atom/isotope lecture notes and a blank sheet of paper. Warm Up: Convert 3.94 inches/hr to meters/sec Convert 54 nL to uL Instructions

X X = = X + = Examples: Formula: .989 12 amu C – 12 = 12 amu .14 amu % abundance of isotope expressed as a decimal Mass of the isotope X Formula: Determine the atomic mass of carbon. The 2 isotopes are C-12 & C-13. % abundance is 98.9 & 1.10. X .989 = 12 amu C – 12 = 12 amu Do the example on worksheet A = .14 amu C – 13 = X 13 amu .0110 + = 12 amu .14 amu 12.14 amu 12 amu

X X = = X + = Examples: Formula: .989 22 amu X – 22 = 22 amu 2.3 amu % abundance of isotope expressed as a decimal Mass of the isotope X Formula: Determine the atomic mass of element X. The 2 isotopes are X-22 & X-23. % abundance is 98.9 & 10.10. X .989 = 22 amu X – 22 = 22 amu Element X is Mg = 2.3 amu X – 23 = X 23 amu .1010 + = 22 amu 2.3 amu 24.3 amu 24 amu

Review: What is the average atomic mass unit for Iron? 55.85 What is the mass # for Iron? 56 What 3 particles make-up the average atomic mass? From lecture notes What 2 particles make-up the mass #?

U 9 10 Example 92 92 238 146 238.03 92 9 F 19.00 19 9 Atomic Number Element/Ion Atomic Number Atomic Mass Mass Number Prot. Neut. Elect. U   9 10 92 92 238 146 238.03 92 9 F 19.00 19 9 From lecture notes

1. The mass # is the sum of ______ & ______. Review Number your paper 1-5 and just write the answer! 1. The mass # is the sum of ______ & ______. 2. An average atomic mass is the sum of what three things? 3. Which subatomic particle identifies an element? 4. Which subatomic particle determines the reactivity of an element? 5. Who discovered the electron? What type of ray did he observe?

instructions? 1. Dalton wrote which theory? Review Answer the following quest. on the blank sheet of paper. 1. Dalton wrote which theory? 2. List the 3 subatomic particles. 3. Which two subatomic particles make-up the nucleus? 4. A negatively charged particle is called an ___________. 5. Draw a circle on your paper, inside the circle draw the nucleus, e-, p+ and n0 for the atom Carbon. instructions?

6. Most of the mass of an atom is found where? Review Directions: # paper 6-10, write just the answer 6. Most of the mass of an atom is found where? 7. Whose theory states that all atoms of the same element are identical? 8. Which experiment led to the discovery of the nucleus? 9. What is the charge on the nucleus? What cancels out this charge? 10. A cathode ray proved the presence of an _____ & a canal ray showed ___ were present in an atom. What piece of equipment was used?

Take out your homework problems instructions?