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Moseley
arranged by nuclear charge (# of protons)
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Periodic Law
Physical and chemical properties of the elements are periodic functions of their atomic numbers
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Modern Periodic Table
arranged by atomic # and similar properties in groups
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Lanthanides
shiny metals similar reactivity to group 2
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Actinides
all radioactive, Th –Np naturally occurring, others laboratory created
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Mendeleev:
grouped elements by similar properties, arranged by increasing atomic mass, left spaces for “unknown” elements
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Periodicity
regular repeating pattern of properties across a period in the PT
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4 blocks of PT
s, f, d, p
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S-block
alkali metals, alkaline earth metals, hydrogen, helium
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Alkali metals
silvery appearance, soft, extremely reactive, MP decreases down the group
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Alkaline earth metals
contain pair of electrons in s sublevel, harder, denser, stronger than alkali metals, very reactive
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Hydrogen
does not share properties with alkali metals, gas at room temp, flammable
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Helium
located in group 18, chemically stable, nonreactive
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Diatomic Molecules
molecules are molecules composed only of two atoms, of either the same or different chemical elements.
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P-block
groups 13-18,includes metals, nonmetals, and metalloids (not including Helium)
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Halogens
Most reactive nonmetals, react with metals to form salts, F and Cl are gases, Br liquid, I and At solids (F, Br, Cl, I exist as diatomic molecules: F2, Br2, Cl2, I2)
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Noble Gases
Nonreactive, inert gases
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Metalloids
brittle solids, some conductivity of electricity but not as much as metals
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P-block metals
harder and denser than s-block, softer and less dense than d-block, stable in presence of air
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F-block
lanthanides and actinides (inner transition metals)
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Atomic radii
radius of atom, indicates volume
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Period trend:
atomic radii (size) decreases across a period from group 1 to group 18
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Group trend
atomic radii (size) increases down a group from period 1 to period 7
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Atomic radius
may be defined as one-half the distance between the nuclei of identical atoms that are bonded together.
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Ion
an atom or group of bonded atoms that has a positive or negative charge.
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Ionization
Any process that results in the formation of an ion
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Ionization energy, IE
The energy required to remove one electron from a neutral atom of an element
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electron affinity
The energy change that occurs when an electron is acquired by a neutral atom
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valence electrons
The electrons available to be lost, gained, or shared in the formation of chemical compounds
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Electronegativity
a measure of the ability of an atom in a chemical compound to attract electrons from another atom in the compound
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