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Alicia Díaz Marcos
STRUCTURE OF AN ATOM
Alicia Díaz Marcos
PARTICLES OF THE ATOM
Particle Charge (C) Mass (g) Mass (U)
Electron -1,6.10-19 9,1.10-28 0,00055
Proton 1,6.10-19 1,673.10-24 1,0076
Neutron 0 1,675.10-24 1,0090
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PARTICLES OF THE ATOM
Particle Charge (C) Mass (g)
Electron m
Proton M
Neutron M
-
+
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ESTRUCTURE OF THE ATOM
PROTONS = p
NEUTRONS = n
+
ELECTRONS = e -
• NUCLEUS
• CRUST
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++
+
-
-
-
ESTRUCTURE OF THE ATOM
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NAME OF THE ATOM
• The elements of the periodic system are representedby 1, 2 or 3 letters
• If only one letter is used, it is written with a capitalletter. Ex: Hydrogen: H; Potassium: K
• If you have more than one letter, the first is writtenwith a capital and the second in lower case. Ex:Aluminium: Al, Sodium: Na
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ATOMIC NUMBER
• Z = Atomic number represents the order ofelements in the periodic table and matchesthe number of protons (if the atom is neutral,it also indicates the number of electrons)
• Z = number of protons = number of electrons
+ -
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MASS NUMBER
• A = Mass number: represents the number ofparticles in the nucleus, i.e. the number ofprotons + the number of neutrons
A = number of protons + number of neutrons
+
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NEUTRAL ATOMS
The same number of protons as electrons
Z = p = eA = p + n
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Examples
Z
A
p = protons
e = electrons
n = neutrons
Li73
Z 3
A 7
p = protons 3
e = electrons 3
n = neutrons 4
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Question
Na2311
Z 11
A 23
p = protons 11
e = electrons 11
n = neutrons 12
Z
A
p = protons
e = electrons
n = neutrons
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Z A p e n
39K19
64Cu29
40Ar18
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Z A p e n
39K19 19 39 19 19 20
64Cu29 29 64 29 29 35
40Ar18 18 40 18 18 22
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ISOTOPES
Atoms with the same atomic number (same number of protons) but different mass number
(different number of neutrons)
Z A p e
12C6 6 12 6 6
14C6 6 14 6 6
n
6
8
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Question
Which of the following represent isotopes of the same element? Which
element?
234 X
234 X
235 X
238 X
92 93 92 92
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Question
Naturally occurring carbon consists of three isotopes, 12C, 13C, and 14C. State the number
of protons, neutrons, and electrons in each of these carbon atoms.
12C6
13C6
14C6
p+
no
e-
12C6
13C6
14C6
p+ 6 6 6
no 6 7 8
e- 6 6 6
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IONS
Atoms that have gained or lost electrons
• Aions: atoms that have gained electrons• Cations: Atoms that have lost electrons
(Note: that the number of protons does not change)
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Z A p e n
55Fe26 26 55 26 26 29
Fe3+ 26 55 26 23 29
33S16 16 33 16 16 17
S= 16 33 16 18 17
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Question
Write the nuclear symbol form for the following atoms or ions:
A. 8 p+, 8 n, 8 e- ___________
B. 17p+, 20n, 17e- ___________
C. 47p+, 60 n, 46 e- ___________
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ELECTRONIC DISTRIBUTION
1s2
2s2 2p6
3s2 3p6 3d10
4s2 4p6 4d10 4f14
5s2 5p6 5d10 5f14
6s2 6p6 6d10
7s2 7p6 7d10
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ELECTRONIC DISTRIBUTION
1s²2s² 2p⁶3s² 3p⁶ 3d¹⁰4s² 4p⁶ 4d¹⁰ 4f¹⁴5s² 5p⁶ 5d¹⁰ 5f¹⁴6s² 6p⁶ 6d¹⁰7s² 7p⁶ 7d¹⁰
1s2 2s2 2p6 3s1
1s2 2s2 2p6 3s2 3p5
1s2 2s2 2p6 3s2 3p6 4s2 3d6
Na ( Z=11)
Cl (Z=17)
Fe (Z=26)
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Question
• Ca (Z=20):1s² 2s² 2p⁶ 3s² 3p⁶ 4s²
• P (Z=15): 1s² 2s² 2p⁶ 3s² 3p³
• Cu (Z=29): 1s² 2s² 2p⁶ 3s² 3p6 4s² 3d⁹