Transcript Regents Unit 8 Periodic Table

What is the periodic table?
• A compact way of organizing the elements
that contains a lot of information and
allows us to make predictions about the
behavior and properties of the elements.
• Elements
History of the Periodic Table
• End of the 1700’s – less than 30 elements
known.
• Many elements were discovered during
the 1800’s. Many experiments were done
to determine atomic masses.
John Newlands - Octaves
• 1864: Newlands noticed that when the
known elements were arranged by atomic
masses, their properties repeated every
8th element.
• Law of Octaves did not work for all known
elements.
• Key idea was correct: Properties of
elements do repeat in a periodic way.
Mendeleev & Meyer
• 1869: Mendeleev produced 1st accepted
periodic table.
• Elements ordered by increasing atomic
mass into columns with similar properties.
• Predicted the existence & properties of
undiscovered elements. (Sc, Ge, Ga)
• Not totally correct. As more accurate
determinations of atomic mass were made,
several elements weren’t in the right place.
Remember
• 1860’s: No subatomic particles had been
discovered yet.
• People were going by Dalton’s billiard ball
model of the atom.
1913 – Henry Moseley
• By 1913, protons & electrons discovered. Neutrons
predicted.
• When cathode rays hit stuff, they produce X-rays.
• Mosely used 30 different elements as “stoppers”
• Found that the greater the atomic weight of the
“stopper,” the shorter the wavelength of the xrays.
What does any good scientist do?
PLOTS THE DATA!
•Tried correlating the wavelength of the x-ray
with the atomic mass of the stopper. Not so
nice. Change in  much more regular than
change in atomic weight.
•Then tried correlating the wavelength of the
x-ray with an integer, n. Got a very pretty
graph.
Atomic Number - 1913
• Mosley interpreted the integer, n, to be the
positive charge on the nucleus.
• Mosley suggested that the size of the
nuclear charge increased by 1 with each
step up the periodic table. (Before, it was
organized by atomic weight.)
1913 – Moseley discovers Atomic #
• Moseley determined that atoms of each
element contain a unique number of
protons – atomic number.
• Moseley rearranged Mendeleev’s periodic
table by atomic number instead of mass.
• Problems disappeared.
Periodic Law
• There is a periodic repetition of chemical
and physical properties of the elements
when they are arranged by increasing
atomic number.
Glenn Seaborg: 1950’s
• Lanthanide and Actinide Series
Vocabulary of the P.T.
• Columns are called groups or families. 2
different notations.
– 1 thru 18, Arabic numerals.
– Split into A & B groups. Use Roman numerals I
to VIII.
• A-Group = Columns 1,2,13-18 = representative
elements
• B-Group = Transition metals
• Rows are called series or periods.
Numbered 1 thru 7.
Structure of the Periodic Table
• Closely related to electron configuration.
Energy Levels = Row Number
• Elements in the same row have the same
number of principal energy levels. (The
valence electrons of same-row elements
have the same principal quantum number.)
• The number of principal energy levels is
equal to the row number.
Going Across Row 2:
Family
IA
IIA
IIIA
IVA
VA
VIA
VIIA
VIIIA
Element
Configuration
2-1
2-2
2-3
2-4
2-5
2-6
2-7
2-8
Li
Be
B
C
N
O
F
Ne
Which atom is the largest?
Li!!
Going Down Column 1:
Period
Element
Configuration
1
H
1
2
Li
2-1
3
Na
2-8-1
4
K
2-8-8-1
5
Rb
2-8-18-8-1
6
Cs
2-8-18-18-8-1
7
Fr
2-8-18-32-18-8-1
Which atom is the largest?
Fr
Valence Electrons
• Elements in the same column have the
same number of valence electrons.
Group
1 or IA
Number of Valence
Electrons
1
2 or IIA
2
13 or IIIA
3
14 or IVA
4
Valence Electrons
• Chemical behavior is determined by the
number of valence electrons.
• Elements with the same number of
valence electrons will have similar
chemical properties.
• Elements in the same column have similar
chemical properties.
Classifying the Elements
• 2/3 of the elements are metals.
• Remaining elements are non-metals and
metalloids (semi-metals).
• Metalloids have some properties of metals
and some properties of nonmetals.
• Know the “staircase” dividing line on the
P.T. between metals & nonmetals.
Everything to left, except H, is a metal.
Properties of Metals
•
•
•
•
•
•
Malleable – pounded into sheets
Ductile – drawn into wires
Have Luster
Good conductors of heat & electricity
Solids at room temperature, except Hg.
Metals lose electrons to form positive ions.
“Metals are losers.”
• Low ionization energy
• Low electronegativity
Properties of Nonmetals
•
•
•
•
•
Generally gases or solids, except Br2.
Solids are brittle.
Solids are dull.
Poor conductors of heat & electricity.
Nonmetals gain electrons to form negative
ions. “Nonmetals are winners.”
• High ionization energy.
• High electronegativity.
• Properties are the OPPOSITE of metals.
Properties of Metalloids
• Each metalloid has some metallic and
some nonmetallic properties.
• For example, Si is shiny like a metal but
brittle like a nonmetal.
Names of Families
•
•
•
•
Group 1 = Alkali Metals (IA)
Group 2 = Alkaline Earth Metals (IIA)
Group 17 = Halogens (XVIIA)
Group 18 = Noble Gases (XVIIIA or O)
– The noble gases are extremely unreactive.
Weren’t discovered until 1890’s.
Transition Metals
• Elements in Columns 3 through 12
• Also called the group B elements
• Transition elements form brightly colored
salts and brightly colored solutions.
• Transition elements may form more than 1
positive ion.
• Actinide and Lanthanide series = inner
transition elements
Elements that are gases at STP
H2, N2, O2, F2, Cl2 + the noble
gases – He, Ne, Ar, Kr, Xe, Rn
Elements that are liquids at STP
Br2 (non-metal) and Hg (metal)
Allotrope
• Different forms of an element in the
same phase. Have different
structures and properties.
• O2 and O3 - both gas phase
• Graphite, diamond, buckey balls – all
solid phase carbon.
C60
Graphite and Diamond