Produced 1st periodic table w/ all known elements. Predicted properties of undiscovered elements. Grouped by similar properties and arranged by increasing atomic mass.
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What did Henry Moseley contribute?
Showed atomic # should be the basis for arranging elements to eliminate discrepancies.
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Periodic Law
Repeating physical and chemical properties of elements change periodically with the atomic #.
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Valence Electrons
The outermost electrons in an atom.
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Which electrons partake in chemical reactions?
Valence Electrons
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Groups
Vertical columns on the periodic table.
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What explains why similar properties appear on the periodic table?
Electron Configurations
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What determines chemical properties?
The number of valence electrons.
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Period
Horizontal row on the periodic table.
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Electron Shielding
Valence electrons are shielded for nucleus by inner electrons.
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What weakens the strength of attraction between the nucleus and valence electrons?
Electron Shielding
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During electron shielding, is the repulsion between the inner and outer electrons?
Yes, the like charges cause them to repel.
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What is the trend for electron shielding across a group?
Increases down a group since the energy levels are increasing.
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What is the trend for electron shielding across a period?
Remains constant
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Effective Nuclear Charge
The strength of attraction between protons in the nucleus and the valence electron with shielding electrons taken into account.
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What is the trend for ENC across a group?
Decreases down groups; due to increase in distance and shielding electrons
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What is the trend for ENC across periods?
Increases across periods; due to additional protons in the nucleus without a change in the electron shielding
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Atomic Radius
Size of the atom; electrons occupy most of the volume
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Why is atomic radius hard to calculate?
Electrons are located in “clouds” with no definite boundaries.
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What is the trend for atomic radius across a group?
Increases down a group; due to electrons occupying additional energy levels which makes the atom bigger.
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What is the trend for atomic radius across a period?
Decreases across a period; additional protons pull electrons closer making the atom smaller.
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Are cations smaller or larger than their neutral atom?
smaller; due to loss of electrons
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Are anions smaller or larger than their atoms?
larger; due to gain of electrons
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Ionization Energy
Energy needed to remove an electron from a neutral atom or an ion.
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What is the trend for ionization energy across a group?
Decreases down a group; due to # of occupied energy levels and electron shielding
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What is the trend for ionization energy across a period?
Increases across a period; addition protons attract electrons.
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Electronegativity
An atom’s attraction for electrons when bonded to another atom.
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What element has the highest electronegativity?
Fluorine
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Do elements with higher electronegativity values hold electrons closer when sharing with another?
Yes
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What is the trend for electronegativity across a group?
Decreases; due to additional energy levels and electron shielding.
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What is the trend for electronegativity across a period?
Increases; due to additional protons
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Electron Affinity
Energy change occurring when a neutral atom attracts an electron
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What is the trend for electron affinity across a group?
Decreases due to electron shielding and a decrease in effective nuclear charge.
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What is the trend for electron affinity across a period?
Increases due to an increases in effective nuclear charge.
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What groups are part of the main-group elements?
1, 2 and 13-18
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What are some properties of metals?
Lusters, good conductors, ductile, malleable, varying melting points, form positive ions, can be mixed with other metals to form alloys
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Are alloy properties different than pure metals?
Yes
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Where are metals located on the periodic table?
Located to the left of the red staircase; metalloids border the red staircase
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What are some properties of nonmetals?
Rarely have luster, gases are room temp., not malleable or ductile, poor conductors, exist as diatomic molecules in elemental form, form negative ions, combine w/ nonmetals to form covalent bonds
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Where are nonmetals located on the periodic table?
Located to the right of the red staircase; metalloids border red staircase
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Metalloids
Properties of metals and nonmetals
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What are some characteristics of metalloids?
look metallic, brittle, not malleable or ductile, not good conductors
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Where are metalloids found on the periodic table?
Bordering the red staircase
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Which group is the alkali metals?
Group 1
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How are alkaline solutions formed?
Alkali metals react with water to form alkaline solutions.
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What make alkali metals very reactive?
They only have one valence electron which they want to lose.
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Why are alkali metals stored in oil?
They have a high reactivity with water and oxygen in the air.
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What are some characteristics of the alkali metals?
soft, easily cut, good conductors
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What is the most reactive metal?
Francium
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Which group is the alkaline earth metals?
Group 2
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Why are alkaline earth metals highly reactive?
They have 2 valence electrons which they want to lose.
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How are alkaline earth metals found in nature?
Found combined with other elements
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What are some characteristics of alkaline earth metals?
harder, higher melting point than alkali metals, good conductors
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Which group are the halogens?
Group 17
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Which is the most reactive group of nonmetals?
Halogens
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Where are Halogens found?
In sea water and rock’s of the Earth’s crust.
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What is the rarest naturally occurring elements?
Astatine
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How are cations formed?
A loss of electrons
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How are anions formed?
A gain of electrons
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What group are noble gases?
Group 18
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Why do noble gases have a low reactivity?
They have a full valence shell.
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Which sublevel contains the transition metals?
d-block
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Do transition metals have identical or unidentical valence electron configurations?
Unidentical
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What is the most common element in nature?
Hydrogen; highly reactive and unique
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What orbitals do lanthanides fill?
4f orbitals
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What orbitals do actinides fill?
5f orbitals
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What are some properties of actinides?
unique and radioactive, unstable nuclei breaks down and releases radioactive waves
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Transuranium Elements
Man-made (synthesized) elements.
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Law of Octaves
When elements are arranged in increasing order of atomic mass, the 8th element resembles the 1st in physical and chemical properties.
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Periodicity
Trends repeated after certain elements when the elements are arranged by atomic number
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