Chapter 19

Chemical Bonds

Section 1: Stability in BondingA. Combined Elements

1. When matter combines chemically, it’s properties change.

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Copper

Copper Sulfate

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B. Formulas

1. Symbols represent a single element

2. Formulas represent the combination of elements called compounds

--Each compound has a “fixed ratio”

--Subscript behind each symbol is the amount of that type of atom

--Numbers in front are how many molecules of that compound *

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PracticeNaCl O2 2CO 2CO2 3H2O

Element or compound?What’s in it?

How many

molecules?

atoms of element?

atoms total?

PracticeSiO2

Sand

Mg(OH)2

Milk of Magnesia

HC2H3O2

Vinegar

3H2SO4

Battery Acid

Element or compound?What’s in it?

How many

molecules?

atoms of element?

atoms total?

C. Atomic Stability

1. Hydrogen and Helium fill the 1st energy level of 2 electrons.

2. All other elements want 8 outer “valence” electrons.

3. Noble Gases – stable; have all 8 valence electrons

--Can predict valance electrons of Groups 1, 2, & 13-18 with Lewis Dot Structure. *

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Electron Dot Practice

He N Cl

Li Ar Al

D. Stability Reached

1. When electrons are gained, lost, or shared between atoms, a chemical bond forms.

2. Chemical bond is an attraction (force) that holds atoms in a compound together.

*

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