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The Atom

The Atom The atom is made up of ____________________________. protons, neutrons, and electrons

PARTICLE SYMBOL MASS(amu) CHARGE Proton p 1. 00 +1 Neutron n 1 PARTICLE SYMBOL MASS(amu) CHARGE Proton p 1.00 +1 Neutron n 1.00 0 Electron e- 0 -1 The proton and neutron have the same mass. All of the mass of an atom comes from the nucleus.

Atomic Number (Z) is the number of protons; this determines the identity of the element. Mass Number (A) the sum of the protons and neutrons. (Round to a whole number). Atomic Mass is the average mass of all the isotopes of the element.

Al 13 13 14 (27-13) K 19 19 20 Pb 82 82 125 ELEMENT PROTONS ELECTRONS NEUTRONS Al 13 13 14 (27-13) K 19 19 20 Pb 82 82 125

Nuclear Symbol Mg 12 12 12 25 30 25 Mn As 33 42 33 Mass # 24 12 Mg 12 12 12 _______ p _______ n _______ e- Atomic # 25 55 30 25 Mn _______ p _______ n _______ e- 25 75 As 33 42 33 _______ p _______ n _______ e- 33

Ions Cations Anions ( + ions) are formed by removing electrons. ( - ions) are formed by adding electrons.

Practice 40 20 +2 20 20 18 Ca _______ p _______ n _______ e- 56 Fe +2 26 30 24 _______ p _______ n _______ e- 26 31 P -3 15 16 18 _______ p _______ n _______ e- 15 - 80 35 Br 35 45 36 _______ p _______ n _______ e-

Isotopes Isotopes are different forms of the same element that have different numbers of neutrons, which gives a different mass. Always add protons and neutrons to find the mass.

Practice 6 6 6 C C 6 8 6 _______ p _______ n _______ e- 12 6 6 6 6 C _______ p _______ n _______ e- 14 C 6 8 6 _______ p _______ n _______ e- 6

Give the nuclear symbol for the particle with: 1. 50 protons, 50 electrons, and 70 neutrons 120 Sn 50 2. 47 protons, 46 electrons, and 63 neutrons 110 + Ag 47

SYMBOL Zr Ba Cs I PROTONS 40 56 55 53 ELECTRONS 40 54 54 54 NEUTRONS 91 40 138 56 +2 135 + 130 - SYMBOL Zr Ba Cs I 55 53 PROTONS 40 56 55 53 ELECTRONS 40 54 54 54 NEUTRONS 51 82 80 77 NET CHARGE +2 +1 -1

Calculating Average Atomic Mass 1. Element X has 2 isotopes. The isotope with a mass of 78.92 amu has a relative abundance of 59.35% and 40.65% have a mass of 80.92 amu. Calculate the average atomic mass of X. = (78.92 amu)(0.5935) + (80.92 amu)(.4065) = 79.73 amu

Calculating Average Atomic Mass 2. Naturally occurring element Z has 3 isotopes. 78.99% have a mass of 24 amu, 10.00% have a mass of 25 amu and 11.01% have a mass of 26 amu. What is the average atomic mass of Z? = (24 amu)(.7899) + (25 amu)(0.10) + (26 amu)(.1101) = 24.32 amu

Nuclear Chemistry

Nuclear Chemistry Energy is stored in the nucleus of the atom. A nuclear reaction is a change that involves the protons and neutrons in an atom. A new element is formed. These reactions gives off energy.

Nuclear Chemistry Becquerel accidently discovered that uranium emits invisible rays.

Nuclear Chemistry Marie and Pierre Curie named the process by which uranium gives off rays radioactivity. They isolated many radioactive elements. This contradicted Dalton’s theory of the indivisible atom. Elements above #82 (Pb) are naturally radioactive.

Marie Curie & Radioactivity https://www.youtube.com/watch?v=w6JFRi0Qm_s https://www.youtube.com/watch?v=TJgc28csgV0

Nuclear Chemistry Three types of radiation that are given off by nuclear reactions are alpha, beta, and gamma.

γ PROPERTY ALPHA BETA GAMMA Composition Symbol Charge Mass (amu) Penetrating Power Shielding High energy radiation He nucleus Electron 4 2 -1 γ He e- +2 -1 4 low moderate very high Very thick lead or concrete Paper, clothing Metal foil

Nuclear Reactions U He + Th Ra He + Rn Alpha Emission 238 92 4 2 234 90 U He + Th 226 88 4 2 222 86 Ra He + Rn

Nuclear Reactions Mg e + Al S e + Cl Beta Emission 27 12 -1 27 13 35 -1 e 27 13 + Al 35 17 35 16 -1 S e + Cl

Nuclear Reactions Gamma Emission 230 90 226 88 4 2 Th Ra + He + γ

Half Life Time it takes for ½ of a radioactive sample to decay. Ex. C-14 has a half life of 5730 years. F-21 has a half life of 5 sec.

Half Life Half life: (1/2)n n = # cycles n = 20/5 = 4 cycles = (1/2)4 1. F-21 has a half life of 5 sec. What fraction of the original nuclei would remind after 20 sec? Half life: (1/2)n n = # cycles n = 20/5 = 4 cycles = (1/2)4 = 0.0625 = 1/16

Half Life Half life: (1/2)n n = # cycles n = 60/5 = 12 cycles B. After 1 minute? (60 s) Half life: (1/2)n n = # cycles n = 60/5 = 12 cycles = (1/2)12 = 2.44 x 10-4 = 1/4096

Half Life Half life: (1/2)n n = # cycles n = 30/5 = 6 cycles = (1/2)6 C. If the original sample of F-21 had a mass of 250mg, how much would remain after 30 sec? Half life: (1/2)n n = # cycles n = 30/5 = 6 cycles = (1/2)6 = 0.0156 = (0.0156)(250 mg) = 3.91 mg

Nuclear Reactions + Ba + Kr 3 n n U + 1 235 92 139 56 94 36 1 Fission: a nuclear reaction in which a nucleus is broken into smaller nuclei. Nuclear power plants use controlled fission. 1 235 92 139 56 94 36 1 + Ba + Kr 3 n n U +

Nuclear Reactions + H He + n H 2 1 4 2 1 3 1 Fusion: a nuclear reaction in which small nuclei join to form larger nuclei. Occurs in the sun and stars. 2 1 4 2 1 + 3 1 H He + n H