1. The Atom

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

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

4. 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.

5. 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

6. 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

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

8. 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-

9. 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.

10. 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

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

12. SYMBOL Zr Ba Cs I PROTONS 40 56 55 53 ELECTRONS 40 54 54 54 NEUTRONS91 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

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

14. Calculating Average Atomic Mass
2. Naturally occurring element Z has 3 isotopes % 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)
= amu

15. 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.

16. Nuclear Chemistry con’t.
Becquerel accidently discovered that uranium emits invisible rays.
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.

17. Action!
Radioactivity TedEd Video

18. Nuclear Chemistry con’t.
Three types of radiation that are given off by nuclear reactions are alpha, beta, and gamma.

19. 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

20. Nuclear Reactions U He + Th Ra He + Rn Alpha Emission 238 92 4 2 23490 U He + Th
226 88 4 2
222 86 Ra He + Rn

21. 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

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

23. 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.

24. 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
= = 1/16

25. 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

26. 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)(250 mg)
= 3.91 mg

27. 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 +

28. 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