Atoms and the Periodic Atoms and the Periodic TableTable

Chapter 8Chapter 8

Homework AssignmentHomework AssignmentChap 8Chap 8

Read p 223 – 231; 236 - 242Read p 223 – 231; 236 - 242

Applying the Concepts (p 243): 1 – 13, Applying the Concepts (p 243): 1 – 13,

15 – 17, 19, 23 - 35, 39 – 44, 46 - 5015 – 17, 19, 23 - 35, 39 – 44, 46 - 50

Dalton’s Atomic Theory (1808)Dalton’s Atomic Theory (1808)(Listed on p 224)(Listed on p 224)

1.1. ElementsElements are composed of extremely small particles are composed of extremely small particles called called atomsatoms. .

2.2. All atoms of a given element are identical, having the All atoms of a given element are identical, having the same size, mass and chemical properties. same size, mass and chemical properties.

3.3. The atoms of one element are different from the atoms of The atoms of one element are different from the atoms of all other elements.all other elements.

4. 4. CompoundsCompounds are composed of atoms of more than one are composed of atoms of more than one element. The relative number of atoms of each element in element. The relative number of atoms of each element in a given compound is always the same.a given compound is always the same.

5. Chemical reactions only involve the rearrangement of atoms. 5. Chemical reactions only involve the rearrangement of atoms. Atoms are not created or destroyed in chemical reactions. Atoms are not created or destroyed in chemical reactions.

Particles in an atom

Cathode Ray Tube

N S

J.J. Thomson, discovered the electron

(1906 Nobel Prize in Physics)

Fig 8.2

1. Atom’s positive charge is concentrated in the nucleus2. Proton (p) has opposite (+) charge of electron (-)

(1908 Nobel Prize in Chemistry)

Fig 8.5 Fig 8.6

atomic radius ~ 1 x 10-10 m

nuclear radius ~ 5 x 10-15 m

Planetary Model of the Atom

“If the atom is the Houston Astrodome, then the nucleus is a marble on the 50-yard line.”

Empty space!

Atomic number (Z) = number of protons in nucleus

Mass number (A) = number of protons + number of neutrons

= atomic number (Z) + number of neutrons

Isotopes - atoms of the same element (X) with different numbers of neutrons in their nuclei

XAZ

H11 H (D)2

1 H (T)31

U23592 U238

92

Mass Number

Atomic NumberElement Symbol

0.72% natural abundance

6 protons, 8 (14 - 6) neutrons, 6 electrons

38 protons, 46 (84 - 38) neutrons, 38 electrons

Do You Understand Isotopes?

How many protons, neutrons, and electrons are in C14

6 ?

How many protons, neutrons, and electrons are in Sr 84

38 ?

Visible light consists of electromagnetic waves

Electromagnetic radiation: emission and transmission of energy in the form of electromagnetic waves.

Speed of light (c) in vacuum = 3.00 x 108 m/s

Fig. 7.2

Fig. 7.3 The Electromagnetic Spectrum

White light is separated into its color

components by a prism

White light is separated into its color

components by a diffraction grating

The tracks of a compact disc act as a diffraction grating,producing a separation of the colors of white light.

Line Emission Spectrum of Hydrogen Atoms

Fig 8.8 Atomic Emission Spectra

7.3

First recorded emission spectrum of the sun (1817)

intensity

wavelength

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)

n (principal quantum number) = 1,2,3,…

Fig 8.10

e-

E = h

E = h

Low energyHigh energy

Egreen > Ered

Fig 9.18

Electron configurations of some atoms

Valence electrons ≡ electrons in outermost shell

Fig 2.9

Metals

• good conductors of heat and electricity

• shiny, ductile, malleable

• all solids with one exception

Nonmetals

• poor conductors

• dull appearance, brittle

• consist of solids, liquids, and gases

Physical Properties of the ElementsPhysical Properties of the Elements

Period

Group

Alkali M

etal

Noble G

as

Halogen

Alkali E

arth Metal

p 237

Chemistry In ActionNatural abundance of elements in Earth’s crust

Natural abundance of elements in human body