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24 Cards in this Set
- Front
- Back
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1700
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13 elements were identified
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1765-1775
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5 new elements discovered
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1829 J.W. ( Johann Wolfgang) Döbereliner
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German chemist
grouped some elements into triads a set of 3 elements with similar properties |
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1869 Dmitri Mendeleev
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Russian chemist
published the first table of elements arranged the elements in order of increasing atomic mass he left spaces in his table for those undiscovered he predicted the missing elements correctly |
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1913 Henry Moseley
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British physicist
determined the atomic number for elements arranged the elements in order of increasing atomic number today's periodic table |
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periodic law
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when elements are arranged by increasing atomic number, properties of the elements tend to repeat
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metals
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to the left of the staircase
80% of all elements good conductors of heat and electricity shiny solid at room temperature ( except mercury) ductile (electric through wires ) malleable (flexible) hammer into thin sheets like aluminum |
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nonmetals
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to the right of the staircase
most are gases some are solids (liquid bromine) poor conductor of electricity and heat solids tend to be brittle |
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metalloids
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touches the staircase (except aluminum and polonium)
have properties of both metals and nonmetals |
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representative elements
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groups 1A to 8A
all the tall people groups 1,2,13-18 |
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transition elements
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transition metals
group B the short people inner transition metals last two rows on the periodic table.. the ones that do enter really fit |
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alkali metals
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group 1
1 valence electron explosive when with water |
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alkaline earth metals
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group 2
2 valence electrons highly reactive |
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halogens
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group 17
7 valence electrons most reactive nonmetal theives reacts with metals to form salts |
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noble gases
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group 18
8 valence electrons not reactive and very stable low density not flammable |
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shielding effect
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"shielding" the nuclear pull on electron
valence electrons are shielded from the pull/charge of the nucleus by all the electrons in between farther down on the periodic table the bigger the shield, the harder to shield |
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,"periodic table"
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the properties of elements repeat
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trend
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a predicable change
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periodic. trend
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properties of the elements repeat and form pattern
allows us to make predictions about the chemical behavior of elements how elements will react with other elements many trends exist in the periodic table. |
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atomic radius
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half the distance between two nuclei of the same atom
size of the atom Down the group - increase the number of energy levels increase across the periods - deceased electrons protons attraction increase toward francium |
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ion
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an atom with a charge
cation- positive charged atoms- metals lost electrons anions- negatively charged - nonmetals. gained electrons |
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first ionization energy
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energy needed to remove an electron from an atom
trend down the group- decrease valence electrons are farther away from the nucleus aross a period - increase the atom becomes more stable with more valence electrons |
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ionic size
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the size off the ion compared to the parent atom
cations ions are smaller than the atom it comes from it lost electrons anions ions are larger then the atom it came from it's gained (stole) electrons |
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electronegativity
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the ability of an atom to attract electrons to itself when bounded to another atom
trend. down a group-decreases same as ionization energy across a period-increases same as ionization energy |
