Atoms and the Periodic table

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Slide 82

Writing Electron-Dot Symbols

Electron-dot symbols for

•groups 1A(1) to 4A(14) use single dots.

· ·

Na · · Mg · · Al · · C ·

·

•groups 5A(15) to 7A(17) use pairs and single dots.

· · · ·

· P · : O ·

· ·

Slide 83

Groups and Electron-Dot Symbols

In a group, all the electron-dot symbols have the

same number of valence electrons (dots).

Example: Atoms of elements in Group 2A(2) each have 2 valence electrons.

· Be ·

· Mg ·

· Ca ·

· Sr ·

· Ba ·

Slide 84

Lewis Dot Structures

Slide 85

Learning Check



A. X is the electron-dot symbol for

1) Na 2) K 3) Al

l 

B. l X l

l is the electron-dot symbol of

1) B 2) N 3) P

Slide 86

Solution

l

A. X is the electron-dot symbol for

1) Na 2) K

 

B. l X l

l is the electron-dot symbol of

2) N 3) P

Slide 87

Chapter Outline

Ionic Bonds

Ionic compounds result from the loss of electrons by one atom (usually a metal) and the gain of electrons by another atom (usually a nonmetal).

Ionic bonds arise from the attraction between particles with opposite charges (electrostatic forces); e.g., Na+ Cl-.

Slide 88

Run the following web animations/movies.

3.7: Ion Formation

Slide 89

Ionic Compounds

Slide 90

Atomic Size

Atomic size is described using the atomic radius; the distance from the nucleus to the valence electrons.

Slide 91

Atomic Radius Within A Group

Atomic radius increases going down each group of representative elements.

Slide 92

Atomic Radius Across a Period

Going across a period left to right,

•an increase in number of protons increases attraction for valence electrons.

•atomic radius decreases.

Slide 93