Studied by 20 peopleWhat did John Newlands contribute?
Discovered the Law of Octaves
What did Dmitri Mendeleev contribute?
Produced 1st periodic table w/ all known elements. Predicted properties of undiscovered elements. Grouped by similar properties and arranged by increasing atomic mass.
What did Henry Moseley contribute?
Showed atomic # should be the basis for arranging elements to eliminate discrepancies.
Periodic Law
Repeating physical and chemical properties of elements change periodically with the atomic #.
Valence Electrons
The outermost electrons in an atom.
Which electrons partake in chemical reactions?
Valence Electrons
Groups
Vertical columns on the periodic table.
What explains why similar properties appear on the periodic table?
Electron Configurations
What determines chemical properties?
The number of valence electrons.
Period
Horizontal row on the periodic table.
Electron Shielding
Valence electrons are shielded for nucleus by inner electrons.
What weakens the strength of attraction between the nucleus and valence electrons?
Electron Shielding
During electron shielding, is the repulsion between the inner and outer electrons?
Yes, the like charges cause them to repel.
What is the trend for electron shielding across a group?
Increases down a group since the energy levels are increasing.
What is the trend for electron shielding across a period?
Remains constant
Effective Nuclear Charge
The strength of attraction between protons in the nucleus and the valence electron with shielding electrons taken into account.
What is the trend for ENC across a group?
Decreases down groups; due to increase in distance and shielding electrons
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
Atomic Radius
Size of the atom; electrons occupy most of the volume
Why is atomic radius hard to calculate?
Electrons are located in “clouds” with no definite boundaries.
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.
What is the trend for atomic radius across a period?
Decreases across a period; additional protons pull electrons closer making the atom smaller.
Are cations smaller or larger than their neutral atom?
smaller; due to loss of electrons
Are anions smaller or larger than their atoms?
larger; due to gain of electrons
Ionization Energy
Energy needed to remove an electron from a neutral atom or an ion.
What is the trend for ionization energy across a group?
Decreases down a group; due to # of occupied energy levels and electron shielding
What is the trend for ionization energy across a period?
Increases across a period; addition protons attract electrons.
Electronegativity
An atom’s attraction for electrons when bonded to another atom.
What element has the highest electronegativity?
Fluorine
Do elements with higher electronegativity values hold electrons closer when sharing with another?
Yes
What is the trend for electronegativity across a group?
Decreases; due to additional energy levels and electron shielding.
What is the trend for electronegativity across a period?
Increases; due to additional protons
Electron Affinity
Energy change occurring when a neutral atom attracts an electron
What is the trend for electron affinity across a group?
Decreases due to electron shielding and a decrease in effective nuclear charge.
What is the trend for electron affinity across a period?
Increases due to an increases in effective nuclear charge.
What groups are part of the main-group elements?
1, 2 and 13-18
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
Are alloy properties different than pure metals?
Yes
Where are metals located on the periodic table?
Located to the left of the red staircase; metalloids border the red staircase
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
Where are nonmetals located on the periodic table?
Located to the right of the red staircase; metalloids border red staircase
Metalloids
Properties of metals and nonmetals
What are some characteristics of metalloids?
look metallic, brittle, not malleable or ductile, not good conductors
Where are metalloids found on the periodic table?
Bordering the red staircase
Which group is the alkali metals?
Group 1
How are alkaline solutions formed?
Alkali metals react with water to form alkaline solutions.
What make alkali metals very reactive?
They only have one valence electron which they want to lose.
Why are alkali metals stored in oil?
They have a high reactivity with water and oxygen in the air.
What are some characteristics of the alkali metals?
soft, easily cut, good conductors
What is the most reactive metal?
Francium
Which group is the alkaline earth metals?
Group 2
Why are alkaline earth metals highly reactive?
They have 2 valence electrons which they want to lose.
How are alkaline earth metals found in nature?
Found combined with other elements
What are some characteristics of alkaline earth metals?
harder, higher melting point than alkali metals, good conductors
Which group are the halogens?
Group 17
Which is the most reactive group of nonmetals?
Halogens
Where are Halogens found?
In sea water and rock’s of the Earth’s crust.
What is the rarest naturally occurring elements?
Astatine
How are cations formed?
A loss of electrons
How are anions formed?
A gain of electrons
What group are noble gases?
Group 18
Why do noble gases have a low reactivity?
They have a full valence shell.
Which sublevel contains the transition metals?
d-block
Do transition metals have identical or unidentical valence electron configurations?
Unidentical
What is the most common element in nature?
Hydrogen; highly reactive and unique
What orbitals do lanthanides fill?
4f orbitals
What orbitals do actinides fill?
5f orbitals
What are some properties of actinides?
unique and radioactive, unstable nuclei breaks down and releases radioactive waves
Transuranium Elements
Man-made (synthesized) elements.
Law of Octaves
When elements are arranged in increasing order of atomic mass, the 8th element resembles the 1st in physical and chemical properties.
Periodicity
Trends repeated after certain elements when the elements are arranged by atomic number
Which elements form cations?
Elements to the left of the red staircase
Which elements for anions?
Elements to the right of the red staircase.
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