key players in modern atomic theory · 2013-09-27 · henry moseley •in 1911, henry moseley...
TRANSCRIPT
Key Players in Modern Atomic Theory
Dead Guy #1 Dalton…1808 5 Postulates
One was incorrect…All atoms of the same element are identical! Should be written: All atoms of the same element have the same number of protons!
Dalton’s Atom Model
Dead Guy #2 Thomson…1897
PLUM PUDDING MODEL!!
Plums = Electrons
Father of the ELECTRON!
Thomson’s Atom Model
Dead Guy #3 Rutherford…1911
Gold Foil Experiment…AKA… Rutherford’s Shooting Gallery
Disproved Thomson’s Plum Pudding Theory
Father of: the POSITIVELY charged NUCLEUS; PROTONS; and
NEUTRONS
Rutherford’s Atom Model
Dead Guy #4 Bohr…1912
Believed the ELECTRONS “orbited” the nucleus like “planets orbit the sun.”
NOT 100% accurate, but the EASIEST model to DRAW/EXPLAIN since it only deals in 2D.
Bohr Atom Model of Carbon
Magic Numbers: 2,8,18…
BOHR MODEL PRACTICE
• DRAW Magnesium
BOHR MODEL PRACTICE
• DRAW Chlorine
Subatomic Particles Review
Lightest to heaviest…ELECTRON, PROTON, NEUTRONS
amu = atomic mass unit
Counting Atoms!
• How Many Atoms are in EACH of the following chemical formulas??
• C6H12O6 =
• NaHCO3 =
• NaClO =
• Na2B4O7 =
• Mg(OH)2 =
• CH3COOH =
• 2NH4H2PO4 =
24
3
13
5
8
24
6
Isotopes
ATOMS OF THE SAME ELEMENT WITH DIFFERENT
NUMBERS OF NEUTRONS (THEREFORE HAVE
DIFFERENT MASSES).
A: Mass Number #protons + # neutrons in the nucleus
Always larger than Z
Writing Isotope Symbols
X: element symbol Z: Atomic
number
#protons
Writing Isotope Symbols
Na 11
23 Sodium-23
Practice Isotope Problem
Write the isotope symbol for the chemical element that has 17 protons and 16 neutrons.
Cl or Chlorine-33 17
33
Practice Isotope Problem #2
How many protons are in the isotope 54Cr? (Chromium-54)
24 (like every atom of
Chromium)
#3 How many neutrons are in the isotope 42Ca?
22 neutrons
#4 How many electrons are in the isotope 23Na?
11 electrons
Workout!
• 1. The______________is the number of protons in the nucleus of an atom.
• 2. The _________________is the sum of the number of neutrons and protons in the ___________of an atom
• 3. The atoms of an element always have the same number of____________.
Atomic number
Mass Number
Nucleus
Protons!!!
Average Atomic Mass…
Atomic Mass/Atomic Weight/Mass Number is ALWAYS listed as a decimal…
WHY??!!
It is an AVERAGE of ALL the KNOWN ISOTOPES of the element…this is WHY Dalton’s Postulate was INCORRECT!!
Practice Filling in the Chart!
When some types of compounds are formed atoms may gain or lose
electrons
ION: an atom that has gained or lost one or more electrons
**atoms with the same atomic
number (number of protons), but
different number of electrons
QUICK SUMMARY TIME!
What is the difference
between ions and
isotopes? What is one
similarity? Difference: Ions deal in changing
ELECTRONS; Isotopes deals in
changing NEUTRONS
Similarity: PROTONS ALWAYS REMAIN
THE SAME!!!!
IONS CATIONS
Typically formed by metals.
Naming Rule:
element ion
ANIONS
Typically formed by nonmetals.
Naming Rule:
root + “ide” ion
POSITIVE IONS NEGATIVE IONS
Quick Check!
If a neutral Magnesium atom loses two
electrons, what will its overall charge be?
A. -2
B. +1
C. +2
D. -1 C
Quick Check!
How many electrons are in an ion of K+1?
A. 39
B. 18
C. 19
D. 20
B
Quick Check!
If a neutral oxygen atom gains two
electrons, what will its overall charge be?
A. -2
B. +1
C. +2
D. -1 A
Quick Check!
How many electrons are in an ion of Br -1?
A. 35
B. 34
C. 36
D. 79
C
History of the Periodic Table
• Mendeleev arranged
the elements in order of
increasing atomic
mass and noticed
that certain similarities
in element’s properties
appeared at regular
intervals
Henry Moseley
• In 1911, Henry Moseley created a periodic
table that was arranged by increasing
atomic number.
How is the PT organized today?
Quick Summary!
What is the main difference
between Mendeleev and
Moseley’s periodic table? What
are some similarities between
the two tables?
Rows (periods): elements are put
in rows by increasing atomic
number Columns (groups): elements are
put into columns (groups) based on
how they react (chemical
properties)
How is the PT ORGANIZED??
Elements in a group are like members of
a family-each is different, but all are
related by common characteristics.
Knowing an element’s group can help us
predict its properties and how it will
react.
Is like….
Physical Properties: solids,
silvery appearance, soft,
shiny
Chemical Properties: undergo
chemical changes easily and
sometimes violently
(especially water)
MOST important fact: the
most reactive metal group
on the periodic table
•don’t occur in nature in their
elemental form
Have 1 VALENCE
ELECTRON
GROUP 1
VERTICAL
COLUMNS
are called
GROUPS
or
FAMILIES
HORIZONTAL ROWS are
called PERIODS.
1
(1VE)
Alkali
Earth
Metals
Physical Properties: solids,
metallic, harder, denser, and
stronger than alkali metals
Chemical Properties: second
most reactive metal group
MOST important fact: less
reactive than alkali metals, but
too reactive to be found in
elemental form
Have 2 VALENCE
ELECTRONS
GROUP 2
VERTICAL
COLUMNS
are called
GROUPS
or
FAMILIES
HORIZONTAL ROWS are
called PERIODS.
1
(1VE) 2
(2VE)
Alkali
Earth
Metals Alkaline
Metals
Physical Properties: very hard,
high boiling point, high
electrical conductivity,
malleable
Chemical Properties: less
reactive than group 1 and 2
metals
MOST important fact: occur in
nature in elemental form
Have 2-3 VALENCE
ELECTRONS
GROUPS 3-12
VERTICAL
COLUMNS
are called
GROUPS
or
FAMILIES
HORIZONTAL ROWS are
called PERIODS.
1
(1VE) 2
(2VE)
3-12
(2-3VE)
Alkali
Earth
Metals Alkaline
Metals
Transition
Metals
Physical Properties:
nonmetals, diatomic
molecules
Chemical Properties: very
reactive, especially with
alkali metals and alkaline
earth metals
MOST important fact: most
reactive group of nonmetals
Have 7 VALENCE
ELECTRONS
GROUP 17
VERTICAL
COLUMNS
are called
GROUPS
or
FAMILIES
HORIZONTAL ROWS are
called PERIODS.
1
(1VE) 2
(2VE)
3-12
(2-3VE)
13
(3VE)
14
(4VE)
15
(5VE)
16
(6VE)
17
(7VE)
Alkali
Earth
Metals Alkaline
Metals
Transition
Metals
Halogens
Physical Properties: gases at
room temperature, when
excited many of the noble
gases give off light
Chemical Properties: Do not
naturally react
MOST important fact: the
most stable group on the
periodic table (exist in
elemental form)
Have 2 or 8
VALENCE
ELECTRONS
GROUP 18
VERTICAL
COLUMNS
are called
GROUPS
or
FAMILIES
HORIZONTAL ROWS are
called PERIODS.
1
(1VE) 2
(2VE)
3-12
(2-3VE)
13
(3VE)
14
(4VE)
15
(5VE)
16
(6VE)
17
(7VE)
18
(2 or 8
VE)
Alkali
Earth
Metals Alkaline
Metals
Transition
Metals
Halogens
Noble
Gases
Has 1 Valence
Electron
HIGHLY Reactive!
Plays a part in 75%
of the known
compounds in the
UNIVERSE!
