Transcript CHAPTER 6: Periodic Table

CHAPTER 6:
Periodic Table
Development of Periodic Table
Mendeleev
1) Contributions – made very
first periodic table
►
2)
p.t. arrangement: elements
ordered by increasing atomic
mass
Development of Periodic Table
3) Noticed periodic pattern (repetition) in
element properties
- elements placed in groups w/ similar
properties
- Left gaps for substances yet to be
discovered
Mendeleev’s Periodic Table (1871)
4) errors: when new elements discovered,
several elements on his table didn’t fit right
- had different properties
Moseley
► periodic
table arrangement: elements
ordered by increasing atomic number
► Periodic
Law – when elements arranged
by increasing atomic number, their physical
& chemical properties show a periodic
pattern
Modern Periodic Table
►
Boxes contain:
1)
2)
3)
4)
Element name
Element symbol
Atomic number
Atomic mass
Modern Periodic Table
► Arrangement
– increasing atomic number
a) groups – columns (vertical)
b) periods – rows (horizontal)
Two Divisions of Elements
► Main
Group Elements – groups 1A, 2A
and 13-18A
(s & p block)
Two Division Of Elements
► Transition
elements
Elements – group 3-12B
(d block)
Classifying Elements
► Metals – elements w/ shine
–
–
–
–
solid @ room temp
conducts heat & electricity
malleable: put into thin wires
ductile: pound into sheets
Metals
a) Alkali Metals – group 1A (except H)
- highly reactive, very soft
b) Alkaline Earth Metals – group 2A
- less reactive and denser than alkali
metals
c) Transition Metals – d-block (group 312B)
Metals
d) Inner transition metals – f-block
i) Lanthanide Series – row 1 of f-block
ii) Actinide Series – row 2 of f-block
La
Ac
Nonmetals
► Defn
- gases or brittle, dull looking solids
- poor conductors of heat & electricity
a) Halogens - group 17A
- highly reactive
b) Noble Gases - group 18A
- very unreactive/stable
Metalloids
► Defn
– BORDER THE STAIRSTEP LINE 
- Have similar chem & phys props as both metals
and nonmetals
Alkaline earth metals
Alkali metals
Lanthanides
Actinides
Halogens
Noble Gases
Transition Metals
Organizing Elements By Electron
Configuration
► Valence
Electron – electrons in highest
energy level
atoms in same group have similar chemical
props b/c they have same # of valence e-
Valence Electrons And Period
► The
period indicates what energy level the
valence electrons are located on
► Ex:
[Ar] 4s2 3d10 4p1
3 Valence eon 4th energy
level
Valence Electrons and Group
Number
►#
of valence electrons equals group number
(only for main group elements)
►
exception: Helium
(in group 18, but has
2 valence e- only)
Ex Problems
► Tell
the group, period, and block where
these elements are located
[Ne] 3s2
[He] 2s2 2p4
[Kr] 5s2 4d105p5
group – 2
group –
group – 17
period – 3
period – 2
period – 5
block – s
block – p
block – p
16
Periodic Trends
► There
are certain patterns that occur with
the elements as you go across and down
the periodic table
which atom is the biggest? smallest?
which atom is most reactive/least stable?
Atomic Radius (size)
► Defn
– distance from center to edge of
electron cloud
► Period
Trend – decreases from left to right
Why?
increasing # of protons (+ charge) in
nucleus has a greater attraction for
electrons (- charge)
Atomic Radius
► Group
Trend – increases from top to bottom
Why?
electrons occupy higher energy levels
and are farther from the nucleus
Period 1
Period 2
Period 3
Atomic Radius
increases
► Summary
decreases
Ion
► Defn
– atom w/ a positive or negative
charge
- atom lost or gained electrons
- # protons ≠ # electrons
Cation
► Defn
– positive ion (atom lost e-)
- more protons than electrons
► Comparing
atom size vs. its cation size
A
A+
atom A
cation of atom A
cations are SMALLER than its original atom
Anion
► Defn
– negative ion (atom gained e-)
- more electrons than protons
► Comparing atom size vs. its anion size
A
atom A
Aanion of atom A
anions are LARGER than its original atom
Ion Summary
A+
cation
<
A
atom
<
Aanion
Ionization Energy
► Defn
– energy required to remove an
electron from an atom
► Period
trend – IE increases from left to right
Why?
increased nucleus charge has greater
hold on valence e-
Ionization Energy
► Group
Trend – IE decreases from top to
bottom
Why?
atomic size increases, valence e- are
farther away so easier to remove (less
energy required)
Period 1
Period 2
Period 3
Ionization Energy
decreases
► Summary
increases
Ex problem
these atoms from increasing to
decreasing ionization energy: Ba, Cs, Cl
increases
decreases
► Rank
Cl
Cs Ba
Cl > Ba > Cs
Electronegativity
► Defn
– relative ability of an atom to attract
electrons in a chemical bond
“how badly does atom want electrons”
while in a bond
► Period
Trend – increases from left to right
► Group Trend – decreases from top to
bottom
Electronegativity
decreases
► Summary
increases
Ex problem
these atoms from high to low
electronegativity: O, Sr, Mg
increases
decreases
► Rank
Mg
O
Sr
O > Mg > Sr