III. Atomic Structure A. Components of atoms + - a) electron, e - (negatively charged), -1.6 x 10...

III. Atomic Structure A. Components of atoms

+

-

a) electron, e- (negatively charged), -1.6 x 10-19 C mass = 1/1838 that of a H atom

Chapter 3

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b) proton, p+ (positively charged) mass mass of H atom

2

Charge and Mass Characteristics of Electrons, Protons, and Neutrons.

c) Neutron, n (no charged) mass mass of H atom

unit charge

electron, e- (negatively charged), -1.6 x 10-19 C

3

atomic number, Z = number of protons in an atom of a given element

mass number, A = # of protons + # of neutrons = (# of nucleons)

d) Symbols of elements

XAZ

Examples

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B. Isotopes Not all atoms of the same element have the same mass

Example: There are 3 kinds of Hydrogen atoms H D T

hydrogen-1 hydrogen-2 hydrogen-3 (protium) (deuterium) (Tritium)

mass ratio 1 2 3

Symbol H H H

1 e-, 1 p+ 1 e-, 1 p+,1 n

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21

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Isotopes: Atoms with the same # of p+s and e-s but different # of n's. They have the same chemical properties except that they are different in mass 5

Examples

Isotopes are atoms of the same element with different number of neutrons.

C C12 6

14 6

All atoms of an element have the same atomic #

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C. Atomic mass (weight) – mass of an atom

Atomic mass unit (amu)

Mass of a H atom = 1.677 x 10-24 g

H11

1 amu

He42 4 amu

Li73 (3p+s,4 ns)

C (6 p+s, 6 ns)12 6

1 amu = 1.667 x 10-24 g

In the periodic table, not all atomic masses (atomic weights) are close to a whole number because of the existence of isotopes.

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Figure 3.3 The periodic table of the elements

Group

peri

od

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Example: Cl

35Cl 37Cl75% 25%

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Alk

ali m

etal

s

Alk

alin

e ea

rth

met

als

Hal

ogen

s

Nob

le g

ases

10

(Main group elements)

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Selected Physical Properties of Metals and Nonmetals.

NonmetalsNonmetals• Except for hydrogen (H), they lie on the right side of the Periodic Table.• Except for graphite, do not conduct electricity.• In chemical reactions, they tend to accept electrons.

MetalsMetals • are solids at room temperature (except for Hg, which is a liquid), shiny, conduct electricity, and are ductile and malleable.

• form alloys (solutions of one metal dissolved in another); brass, for example, is an alloy of copper and zinc

• In chemical reactions, they tend to give up electrons.

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MetalloidsMetalloids

• They have some of the properties of metals and some of nonmetals; for example, they are shiny like metals but do not conduct electricity.

• Six elements are classified as metalloids: boron, silicon, germanium, arsenic, antimony, and tellurium.

• One of the metalloids, silicon, is a semiconductor; it does not conduct electricity under certain applied voltages, but becomes a conductor at higher applied voltages.

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Tc

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D. The inner structure of the atom

Rutherford’s experiment

Observations1. Most of them ( particles) went right through

2. A few deflected3. Some bounced back from the gold foil

He2+

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http://video.google.com/videoplay?docid=-1909836802101196671&q=rutherford+experiment&total=8&start=0&num=10&so=0&type=search&plindex=0

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IV. Electron configuration of atoms

A. Experimental facts (Flame test)

A pure substance absorbs only certain energies andemit certain energies.

From quantum mechanical calculations, electrons canbe in discrete energy levels only

Bohr

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IV. Electron configuration of atoms

A. Experimental facts

A pure substance absorbs only certain energies andemit certain energies.

From quantum mechanical calculations, electrons canbe in discrete energy levels only

Bohr

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B. Energy levels

2 818

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Energy levels

a) Shells and subshells

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b) Orbitals Further studies indicate that electrons do not travel in circles

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Standing wave

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p orbitals

z

24

d orbitals

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Figure3.10

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c) Electron Spin

An electron in an orbital can either spin up or spin down

spin up

Spin down

N

S N

S

A spinning electrongenerates a tiny magnetic field

When their tiny magneticfields are aligned N-S, theelectron spins are paired

1

2

electron pair27

Electron Configuration and Orbital Diagrams

1s

2s

2p

3s

3p

H 1s 1

Orbital (box) diagram Electron configuration

He 1s 2

Pauli exclusive principle

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Electron Configuration and Orbital Diagrams

1s

2s

2p

3s

3p

Orbital diagram Electron configuration

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1s

2s

2p

3s

3p


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Copyright © Houghton Mifflin Company. All rights reserved. 3–13

Figure 3.11 The order of filling of various electronsubshells is shown on the right-hand side of this diagram. Above the 3p subshell,subshells of different shells "overlap".

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1s

2s

2p

3s

3p

Orbital (box) diagram Electron configuration

4s

3d

4p

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1s

2s

2p

3s

3p

4s

3d

4p

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Figure 3.12 The order for filling electronsubshells with electrons follows the order given by the arrows in this diagram. Start with the arrow at the top of the diagram and work toward the bottom of the diagram, moving from the bottom of one arrow to the top o the next-lower arrow.

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1s

2s

2p

3s

3p


4s

3d

4p

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Figure 3.13 Electron configurations and the positions of elements in the periodic table.

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3d

4d5d6d

4s

5s6s

7s

2s

3s

2p

3p

5p6p

4f

5f

4p

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3d

4d5d6d

4s

5s6s

7s

2s

3s

2p

3p

5p6p

4f

5f

4p

Os 1s22s22p6…………… 5d6

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III. Atomic Structure A. Components of atoms + - a) electron, e - (negatively charged), -1.6 x 10...

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