Research Chem Unit 3 - Periodic Table
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31 Terms
Dimitri Mendeleev
1869
developed first periodic table
expressed regularities as a periodic function of the atomic mass
Henry Moseley
revised Mendeleev periodic table by describing regularities as periodic functions of atomic number
Group/family
vertical columns
elements with similar valence electrons configurations
group
number of the column
family
name of elements in a group (eg. alkali metals, noble gases, etc)
Group 1
Alkali metals - high reactivity
Group 2
Alkaline earth metals - high reactivity
Group 3-12
transition metals - low to moderate reactivity
Group 15
Nitrogen family - moderate reactivity
Group 16
oxygen family - reactive
Group 17
halogens - extremely (highest) reactive
Group 18
noble gases - nonreactive
periods
horizontal rows
principle quantum # of valence electrons
metals
left of staircase
lustruous
malleable
ductile
good conductors
nonmetals
right of staircase
non-lustrous
brittle
poor conductors → good insulators
most are gases
metalloids
on staircase
properties of both
s sublevel
1 orbital (2 electrons)
p sublevel
3 orbitals (6 electrons)
d sublevel
5 orbitals (10 electrons)
f sublevel
7 orbitals (14 electrons)
Aufbau Principle
Electrons fill the lowest energy levels first
Pauli Exclusion Principle
each orbital can hold two electrons with opposite spins
Hund’s Rule
all orbitals within a sublevel must contain at least one electron before any orbital can have two
Valence electrons
electrons in the outermost principal energy level (highest coefficient = valence energy level)
core electrons
innermost electrons - not involved in bonding
Isoelectronic
atoms or ions that have the same electron configuration
Electromagnetic Radiation
forms of energy that move through space as waves (eg: light, x-rays, ultraviolet light, infrared, radio waves)
Wavelength
distance between peaks of adjacent waves
Frequency
the number of waves passing a given point in one second
How are photons emitted?
when an electron falls from an excited state to a lower principal energy level (ground state).
periodic table trends
