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Valence electrons
have the highest energy level and held most loosely
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Valence electrons determine
many properties of that element, including ways in which atom can bond to other atoms
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What is the range of valence electrons an atom can have?
1-8
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Electron dot diagram
each dot stands for one valence electron
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How many valence electrons make an atom most stable
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Unreactive elements with high valence electrons do not easlily form_____
compounds
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Chemical bond
force of attraction that holds 2 atoms together as a result of the rearrangement of electrons between them.
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Atoms react to make each atom more stable in one of 2 ways
- 1. the number of valence electrons increases to 8
- 2. the atom gives up loosely held valence electrons
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When atoms bond, one of two things happens witht the electrons
- 1. electrons may be transferred from one atom to another
- 2. electrons may be shared between the atoms
- Both result in a chemical reaction where a new substance forms
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Elements within a group or column of the periodic table have what in common?
the same number of valence electrons
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Why do elements within the same group have similar properties
they have the same number of valence electrons
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Noble Gases group # and valence electron #
- 1. group 18 elements
- 2. 8 except helium has 2
- STABLE
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Halogens - group # and # of valence electrons
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What elements do halogens react with and how
easily react with elements that can give up or share electrons
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Alkali Metals group # and how many electrons
- group 1
- only 1 valence electron
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Are alkali metals reactive? Why?
Very, they can become stable by losing their one valence eletron
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Groups of metals and reactivity pattern
- Groups 1-12
- reactivity of metals decreases from left to right
- Groups 1-2: reactivity increases from top to bottom
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Green section of periodic table is what, and most act like what at room temp
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Zigzag line between metal and nonmetals and range of electrons
- Metalloids
- 3-6
- can behave as metals or nonmetals
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Hydrogen - # of ve's, classification
Reactive yes or no
- Only one valence electron
- Non metal
- reactive
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Most reactive element known
fluorine, can even combine with noble gases
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Ion
- Atom with electric charge
- gaining an electron - negative
- loses electron - positive
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Polyatomic ions
made of more than one atom
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Ionic bond
attraction between 2 oppositely charged ion. Forms as a result of the attraction between positive and negative ions
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Ionic compound
consists of positive and negative ions such as sodium chloride
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Chemical formula
combination of symbols that shows the ratio of elements in a compound.
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when ionic compounds form what happens
- ions come together in a way that balances out the charges on the ions
- chemical formula for the compound reflects its balance
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subscript
tells ratio of elements in the compound
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what comes first in ionic compound name
positive ion, then negative
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Ionic Compounds characteristics in general
hard brittle crystals that have high melting points and conduct electricity when dissolved in water
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crystal
Orderly 3D arrangement
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covalent bond
chemical bond formed when 2 atoms share electrons
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what type of atoms usually form covalent bonds
nonmetals
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what is the force that holds atoms together in cb?
attraction of each atom's nucleus for the shared pair of electrons
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molecule
neutral group of atoms joined by covalent bonds
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double bond
when 2 atoms share 2 pair of electrons
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triple bond
when atoms share 3 pairs of electrons
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molecular compound
composed of molecules and contains atoms that are covalently bonded
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molecular compound characteristics
- lower melting and boiling points
- do not conduct electricity when dissolved in water
- than ionic compounds
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polar bond
covalent bond where electrons are shared unequally
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non polar bond
shared equally
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Columns on the periodic table are called
Groups or families
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Columns in periodic table have what characteristic
Similar propeties
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Most metals are NOT
liquid at room temperature!
- They ARE
- malleable
- reactive
- magnetic (most are)
- shiny
- ductile
- conductive
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the destruction of metal by reacting to oxygen in the air and forming reddish brown rust is called
corrosion
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Which group contains the most elements?
Metals
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The elements that do not usually form compounds are
Noble gases
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Magnesium bromide is an ionic compound with the chemical formula MgBr2. What does the 2 tell you
There are 2 bromide ions for every magnesium ions
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A chemical bond formed when 2 atoms share electrons is called
covalent bond
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Where are metals located on periodic table
to the left of zigzag line
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How do metals react
by losing electrons
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Are alkali metals ever found uncombined in nature
No
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Properites of Alkaline Metals
- never uncombined in nature
- soft shiny
- very reactive
- lose one electron
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Alkaline Earth Metals
- Fairly hard
- Gray white
- Lose 2 electrons
- Good conductor
- Less reactive than group 1 but more than to the right
- never uncombined
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What groups do ionic bonds form between
metals and nonmetals
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covalent compounds form between what group
Non metals
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