CHAPTER 4 NOTES
SECTION 1
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VALENCE e-: an e- in the outermost energy level with the most energy
a. Determine the element’s properties
b. Elements in the same family have the same number of valence ec. Metals: lose e- when they combine with other elements
d. Nonmetals: gain or share e- when they combine with other elements
e. Metalloids: lose or share e- when they combine with other elements
f. Elements in each group have similar properties
E- DOT DIAGRAM: the chemical symbol surrounded by dots that represent the valence eSTABLE ELEMENT: has a full outer level of valence e- (typically 8)
a. This makes the element nonreactive
BONDING: joining of atoms by valence ea. Lose, gain or share valence eCHEMICAL BOND: the force of attraction that holds atoms together
a. As a result of the rearranging of valence e-
SECTION 2
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ION: an atom or group of atoms with an electrical charge
a. Lose an e- to become a positive ion
b. Gain an e- to become a negative ion
POLYATOMIC ION: ions made of 2 or more atoms
IONIC BOND: the attraction between 2 oppositely charged ions (positive and negative)
IONIC COMPOUND: a compound made of positive and negative ions
a. The positive and negative charges are equal and therefore the compound charge is neutral
CHEMICAL FORMULA: a group of symbols that shows the ratio of elements in a compound
a. MgCl2 (1 magnesium atom; 2 chloride atoms)
SUBSCRIPT: the number that tells the ratio of elements in a compound
FORMULAS FOR IONIC COMPOUND
a. The positive ion comes first
b. The negative ion comes second
c. Add subscripts to balance the charges
d. Do NOT write a subscript of 1, it is understood to be 1
NAMING IONIC COMPOUNDS
a. The name of the positive ion comes first
b. The name of the negative ion comes second (1 element change end of name to –ide;
polyatomic change the end of the name to –ite or –ate)
PROPERTIES OF IONIC COMPOUNDS
a. Hard
b. Brittle
c. Crystal: orderly 3-D arrangement of atoms, forms a repeating pattern
d. High melting point: takes a high temperature to break the strong bonds between the positive
and negative ions
e. Conduct electricity when dissolved in water: when dissolved the ions are free to move
around and conduct electricity
f. Strong bonds
SECTION 3
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COVALENT BOND: bonds formed when 2 atoms share electrons
a. Nonmetal +nonmetal
MOLECULE: a neutral group of atoms joined by covalent bonds
SINGLE BOND: when the atoms share 1 pair of eDOUBLE BOND: when atoms share 2 pair of eTRIPLE BOND: when atoms share 3 pair of ePROPERTIES OF MOLECULAR COMPOUNDS
a. Poor conductors of electricity: usually used as insulators
b. Low melting point: weak bonds are broken easily
c. Low boiling point: weal bonds are broken easily
d. Weak bonds
NONPOLAR BONDS: covalent bonds that share e- equally
POLAR BONDS: covalent bonds that share e- unequally
VAN DER WAALS FORCES: the force of attraction between atoms in a polar bond, between the
slightly negative and slightly positive charges
a. Pulls water molecules toward each other
b. Allows the Gecko’s feet to grip onto a smooth surface
SECTION 4
1.
PHYSICAL PROPERTIES: properties that can be observed without changing the substance into
another substance
a. Temperature
b. Color, texture, density
c. Conductivity
2. CHEMICAL PROPERTIES: properties that describe the ability to change into another substance
a. Flammability
b. Reacting with oxygen
c. Reacting with water
3. PHYSICAL CHANGES: any change that alters the form or appearance but does not change the
material into another substance
a. Cutting, bending, crushing
b. Freezing, melting, boiling
4.
CHEMICAL CHANGES(CHEMICAL REACTION): a change in matter that produces 1 or more new
substances
a. Atoms rearrange to form a new substance
b. Burning
c. Rusting, tarnishing
d. Rotting, spoiling
e. Occurs when existing bonds break and new bonds form
f. Atoms gain, lose or share valence eg. REACTANTS: undergo the chemical change
h. PRODUCTS: the new substances formed in chemical reaction
5. CHANGES IN PROPERTIES INDICATES A CHEMICAL REACTION HAS OCCURRED
a. Physical changes
1) Change in texture
2) Change in hardness
3) Change in color
4) Giving off a gas
5) A precipitate forms
b. Chemical changes
1) Changing from reactive to stable
2) Spoiling, molding, rotting
c. PRECIPITATE: a solid formed by combining 2 liquids
6. CHANGES IN ENERGY
a. Breaking bonds uses energy
b. Forming bonds releases energy
c. EXOTHERMIC REACTION: a chemical reaction that releases energy
1) Usually releases energy in the form of heat, light, sound
2) Burning a candle
d. ENDOTHERMIC REACTION: a chemical reaction that absorbs energy
1) Absorbs heat, so the reaction feels cold
2) Combining baking soda and vinegar
SECTION 5
1.
CHEMICAL EQUATION: shows a chemical reactions using symbols and numbers instead of words
to summarize the reaction
a. Chemical symbols, chemical formulas, subscripts, coefficients
2. LAW OF CONSERVATION OF MASS: during a chemical reaction matter is not created or
destroyed
a. All atoms at the beginning of the reaction are present at the end of the reaction
b. Atoms are just rearranged to make new substances
3. OPEN SYSTEM: matter can enter from or escape to the surroundings
a. Fish bowl
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b. Camp fire
CLOSED SYSTEM: matter does not enter or leave the system
a. Inside a sealed, airtight container
b. Terrarium
BALANCING CHEMICAL EQUATIONS:
a. COEFFICIENT: a number placed in front of a chemical formula in an equation
1) Tells the amount of reactant or products
2) Applies to every atom of the formula
SYNTHESIS REACTION: when 2 or more substances combine to form a more complex substance
DECOMPOSITION REACTION: when compounds break down into simpler substances
REPLACEMENT REACTION: when 1 element replaces another in a chemical reaction or when 2
elements trade places in a chemical reaction