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STRUCTURE OF AN ATOM

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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