Chapter 8Chapter 8

Atoms andAtoms andPeriodic PropertiesPeriodic Properties

22

Revised Homework for Chap 8Revised Homework for Chap 8

Read p 203 – 215, 218 – 225

(omit Wave Mechanics,

The Quantum Mechanics Model, and

Electron Configuration)

Applying the Concepts # 1 – 17, 23 - 30

3

Line Emission Spectrum of Hydrogen Atoms

Atomic Emission Spectrum (Line spectrum)

47.3

5

Chemistry in Action: Element from the Sun

In 1868, Pierre Janssen detected a new dark line in the solar emission spectrum that did not match known emission lines

In 1895, William Ramsey discovered helium in a mineral of uranium (from alpha decay).

Mystery element was named Helium

6

1. e- can only have specific (quantized) energy values

2. light is emitted as e- moves from one energy level to a lower energy level

Bohr’s Model of the Atom (1913)

En = E1

n2

n (quantum number) = 1,2,3,…

7.3

7

E = hf

E = hf

7.3

R O Y G B I V

LowLowenergy,energy,

lowlowfrequencyfrequency

HighHighenergy,energy,

highhighfrequencyfrequency

88

Why is e- energy quantized?

9

Standing or stationary wavesStanding or stationary waves

Fig. 5.22Fig. 5.22

nodes nodes

10

De Broglie (1923) reasoned that e- is both a particle and a matter wave!

v = velocity of e-

m = mass of e-

Why is e- energy quantized?

mvh

λ

allowed

matter

wave

forbidden

matter

waveAny moving object

has matter wave properties

Fig 8.13

11

What is the de Broglie wavelength (in m) associated with an 90 kg chemistry professor and his bike riding at 15 m/s?

Impossibly too small to measure!

mvh

λ

m/s) (15 kg) (90sJ 10 x 6.63

λ-34

m 10 x 4.9λ 37

128.2

Classification of the ElementsFig 8.19

Representative elements

Alk

ali m

eta

lsA

lkali m

eta

lsA

lkalin

e e

art

h m

eta

lsA

lkalin

e e

art

h m

eta

ls

Transition metalsTransition metals

Halo

gen

sH

alo

gen

s

Nob

le g

ases

Nob

le g

ases

Metals Nonmetals

13

Chemistry in Action: Discovery of the Noble Gases

Sir William Ramsay

18941868 18981898 1898

sun

new inactive

hidden

stranger

1414

Physical properties of metalsPhysical properties of metals

• high lusterhigh luster

• electrical and thermal conductivityelectrical and thermal conductivity

• malleabilitymalleability

• ductilityductility

Physical properties of nonmetalsPhysical properties of nonmetals

• dull appearancedull appearance

• poor conductorspoor conductors

• brittlebrittle

Fig 8.20 Electron dot notation for representative

elements

Dots represent electrons inoutermost shell

1

5 6 7

8

3 42

Fig 8.21 Location of metals, nonmetals, and

semiconductors

Metal atoms lose one or more electrons

Nonmetal atoms gain one or more electrons

Fig 8.22(A) Metals lose outer electrons

Fig 8.22(B) Nonmetals gain outer electrons