Defining the Atom Atomic Structure - Yolaholcombslab.yolasite.com/resources/Unit 2 atomic structure with... · Atomic Structure 2 Defining the Atom ... credited with discovering the
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9/18/2012
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Atomic Structure
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Defining the Atom
Atom – smallest particle of an
___________ that retains the
chemical __________ of that
element
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Defining the Atom
The Greek philosopher Democritus (460
B.C. – 370 B.C.) was among the ______
to suggest the existence of ________ (from the Greek word “atomos”)
He believed that atoms were indivisible and
indestructible
His ideas did agree with later scientific
theory, but did not explain chemical
behavior, and was not based on the
scientific method – but just _____________ 4
Dalton’s Atomic Theory (experiment based!)
1) Atoms of different elements combine in
simple whole-number ratios to form
chemical _____________
2) In chemical reactions, atoms are combined,
separated, or rearranged – but __________
changed into atoms of another element.
1) All elements are composed of
tiny indivisible particles called
__________
2) Atoms of the same element are
__________. Atoms of any one
element are ___________ from
those of any other element.
John Dalton
(1766 – 1844)
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Sizing up the Atom Elements are able to be subdivided into
smaller and smaller particles – these are
the ___________, and they still have
___________ of that element
If you could line up 100,000,000
copper atoms in a single file, they
would be approximately 1 cm long
Despite their small size, individual
atoms are observable with instruments
such as scanning tunneling (electron)
microscopes 6
Structure of the Atom
One change to Dalton’s atomic theory is that atoms are ___________ into subatomic particles:
____________, _________, and ____________ are examples of these fundamental particles
There are many other types of particles, but we will study these three
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Thomson’s Atomic Model
Thomson believed that the electrons
were like plums embedded in a
_________ charged “pudding,” thus it
was called the “____ pudding” model.
J. J. Thomson
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Although Thompson had the
positive and negative particles in
the wrong place, he is credited
with discovering ___________.
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Earnest Rutherford’s
Experiments
a) The nucleus is _______
b) The nucleus is _______
c) The nucleus is __________
charged
Conclusions:
This “fixed” Thompson’s plum
pudding model. Rutherford is
credited with discovering the
______________. 10
The Rutherford Atomic Model Based on his experimental evidence:
The atom is mostly _________ space
All the positive charge, and almost all the
_______ is concentrated in a small area in
the ________. He called this a “nucleus”
The nucleus is composed of _______ and ___________ (they make the nucleus!)
The ____________ distributed around the
nucleus, and occupy most of the _________
His model was called a “nuclear model”
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Bohr Model
Neils Bohr discovered _______ _______
of electrons. He said that electrons
orbited the nucleus like planets orbit the
___…he was wrong about the orbiting but
right that there are particular energy levels
that electrons reside in.
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Modern (Wave) Model of the Atom
The modern model of the atom consists of
__________ that electrons move around
in…we will discuss later.
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About Atoms
There are presently ___ elements, thus 118 _________ kinds of ________.
These atoms _________ in many different combinations and proportions to form the tremendous number of ___________ found.
Experiments determined that atoms contain three ______________ particles: protons, neutrons, and electrons.
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Atoms have a positively charged dense central core called a nucleus. The nucleus contains protons and neutrons.
Protons – __________ charge
Neutrons – _________ or zero charge
Protons and neutrons have about the same mass.
Electrons move in the space around the nucleus called the _______________.
Electrons – _________ charge
Electron’s mass is _____ _____ ____ than that of neutrons and protons.
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The nucleus is much more __________
but much ___________ than the electron
cloud. If you made a model of an atom to
scale – use __________ as nucleus, the
end of the atom would be 2 ___________
fields away from the baseball.
abbreviations commonly used: p+, no, e-
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Subatomic Particles
1.675 x 10-24 g
__ amu
Neutron
(no)
1.673 x 10-24 g
__ amu
Proton
(p+)
9.11 x 10-28 g
Approx. _ amu
Electron
(e-)
Location Mass (g) and
Mass (amu)
Charge Particle
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Atomic Number – tells the number of _______ in an atom. It is found on the periodic table.
Ex: there are __ protons in an atom of Nitrogen, there are ___ protons in an atom of Uranium
The number of ________ in an atom makes the atom what it is! Ex. Potassium has 19 protons it can never have any more or any less and still be potassium.
Individual atoms are electrically _________, which means they have the _____ number of ________ as __________. Ex. An atom of copper has ___ protons and ___ electrons.
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Mass Number – ____ of _______ and
___________ of a particular atom.
Ex. “Chlorine-37” Ex. “Aluminum-27”
Atomic number: Atomic number:
Mass number: Mass number:
p+: p+:
e-: e-:
no: no:
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Naming Isotopes
The number written after an
element name is always the
______ number for a particular
isotope of that atom.
carbon-12
carbon-14
uranium-235 20
Mass Number
Mass number is the number of
protons and neutrons in the nucleus
of an isotope: Mass # = p+ + n0
- 31
-
Oxygen -
Mass # e- n0 p+ Nuclide
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Arsenic 75
Phosphorus
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Question: Why do you think the “mass” number only includes protons and neutrons?
Answer: because protons and neutrons both have a mass of __ amu, but electrons have a mass of __ amu
Question: Why do you think the mass number is always a whole number?
Answer: because there are always ________ numbers of protons and neutrons in an atom
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Complete Symbols
Contain the symbol of the element,
the mass number and the atomic
number.
X Mass
number
Atomic
number Subscript →
Superscript →
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Symbols
Find each of these:
– number of protons
– number of
neutrons
– number of
electrons
– Atomic number
– Mass Number
Br 80
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Symbols
If an element has an atomic
number of 34 and a mass
number of 78, what is the:
– number of protons
– number of neutrons
– number of electrons
– complete symbol
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Symbols
If an element has 91
protons and 140 neutrons
what is the
– Atomic number
– Mass number
– number of electrons
– complete symbol 26
Symbols
If an element has 78
electrons and 117 neutrons
what is the
– Atomic number
– Mass number
– number of protons
– complete symbol
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Isotopes
Dalton was wrong about all elements of the same type being _____________
Atoms of the same element can have ___________ numbers of __________.
Thus, different _________ numbers.
These are called isotopes – atoms with the same number of protons but different number of neutrons...thus they have different masses.
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Isotopes
Elements occur in _________ as
____________ of isotopes.
Ex. Chlorine exists as chlorine-__ and
chlorine-__. Both have __ protons
but one has __ neutrons and one has
__ neutrons.
•There is no way of predicting which
isotopes exist for each element; these
have been _______________ determined.
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Atomic Mass How heavy is an atom of oxygen?
It depends, because there are different ________ of oxygen atoms.
We are more concerned with the average atomic mass. (this number is found on the (______ _________
This is based on the _____________ (percentage) of each variety of that element in _________.
We don’t use ________ for this mass because the numbers would be too small.
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Measuring Atomic Mass
Instead of grams, the unit we use is the Atomic Mass Unit (_____)
Each isotope has its own atomic mass, thus we determine the average from percent abundance, which is why it is a ___________ and not a _________ number.
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Atomic Masses
<0.01% 6 protons
8 neutrons
14C Carbon-14
1.11% 6 protons
7 neutrons
13C Carbon-13
98.89% 6 protons
6 neutrons
12C Carbon-12
% in nature Composition of
the nucleus
Symbol Isotope
Atomic mass is the average of all the
naturally occurring isotopes of that element.
Carbon = 12.011 32
To get the “most __________
mass number”, __________ the
atomic mass off to the nearest
whole number.
Example: What is the most
common mass number of the
following? Ag, Cu, C, Cl
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Draw models of lithium-5, lithium-6, and
lithium-7 atoms including the correct
numbers of protons, neutrons, and
electrons in each.
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IONS
Ion – atom that has _______ or ____ electrons
Two types:
_________ – a positive ion, one that has
_______ electrons
_________ – a negative ion, one that has
_________ electrons
Atoms NEVER gain or lose __________ or
____________ (except in nuclear reactions)
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Examples
Mg is a magnesium atom and has ___ protons
and ___ electrons so the overall charge is ____.
Mg+2 is a magnesium ion and has ___ protons
and ___ electrons so the overall charge is ____.
Cl is a chlorine atom and has ___ protons and
___ electrons so the overall charge is ____.
Cl- is a chlorine ion has ____ protons and
___ electrons so the overall charge is ____.
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Examples:
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Energy Levels
Who was the first to notice that the electron cloud
has different regions where electrons reside?
There are various ______________ in an electron
cloud. Within each energy level there are
_____________ and within each sublevel there are
__________. Each orbital can hold up to two
electrons.
Electrons move very ________ within their own
______________.
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Maximum number of electrons
Energy levels (n) can
hold a maximum number
of 2n2 electrons.
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6
5
4
3
2
1
Max num
of e-
Energy
level
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More about energy levels…
The total number of __________ levels an atom has corresponds to the _________ number of the atom.
Periods are the ______________ rows on the PT
Ex. An atom of bromine has ___ energy levels because it is in period ___
The ______ energy level, called the ____________ shell, can hold ONLY up to ______ electrons.
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Valence Electrons
_____________ electrons are the electrons in
the __________ energy level.
The atoms are arranged on the periodic table so
that the ones with ___________ properties all
line up in a ____________ or __________.
The ____________ of valence electrons plays a
big role in how the atom _____________.
41 Except He (2) 18 (8A)
17 (7A)
16 (6A)
15 (5A)
14 (4A)
13 (3A)
3-12 and the actinides and
lanthanides (B’s)
2 (2A)
1 (1A)
Number of Valence e- Group Number
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Electron dot diagrams
Use the number of valence electrons as _______
and space them around the ________ sides of
the element’s symbol then ________ up as
needed
Examples:
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Group/Family Names to Label
Alkali Metals
Alkaline Earth Metals
Transition Metals
Lanthanides
Actinides
Boron Family
Carbon Family
Nitrogen Family
Oxygen Family
Halogens
Noble Gases
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Periods
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Ion Charge Prediction
Octet rule – atoms will ________, _________ or share electrons so that they have a ______________ ________________ shell
That's ____ electrons for everything except 1st shell (H and He) which only holds __ electrons
Ex. Nitrogen has ___ valence electrons so it will gain ___ to make ___. N-3
Ex. Sodium has___ valence electron so it will lose that one and the _________ shell becomes the valence shell with ___ electrons. Na+
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Group 1 (1A) makes ____
Group 2 (2A) makes ____
Group 3-12 (B's) are __________________
Group 13 (3A) makes ____
Group 14 (4A) makes ____
Group 15 (5A) makes ____
Group 16 (6A) makes ____
Group 17 (7A) makes ____
Group 18 (8A) makes ____ (doesn't form ions!) why?
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Examples:
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Electron Configurations
AUFBAU principle – electrons fill orbitals starting with the _____________ energy orbital available before filling higher energy orbitals.
PAULI EXCLUSION principle – each orbital can hold at most _ electrons and they must have _______ spins (clockwise and couterclockwise)
HUND'S rule – electrons occupy equal-energy orbitals so that a maximum number of _______ electrons results ex. __ __ __ not __ __ __ **spread out before pairing up**
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Sublevels: s, p, d and f
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Orbitals
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Writing electron configurations
Use the periodic table as a guide.
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More Electron Configurations
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Abbreviated Electron Configurations
Use the previous _______________ to shorten the electron configuration.
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Orbital Notation
Use ________ to represent electrons.
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Exceptions to Orbital Fill Order
Any electron configuration that ends in ____ is too ___________ and actually takes an electron from the previous ___ sublevel and becomes ____.
Example:
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Another Exception
Any electron configuration that ends in ____ is too ___________ and actually takes an electron from the previous __ sublevel and becomes _____.
Example:
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Examples:
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Absorption and Emission
Normally, electrons in an atom are in the ____________ state, which means they are in the _______________ possible energy levels.
However, these electrons can be ___________ to higher energy levels if energy is added...called _________________.
If energy is absorbed and the electrons jump to higher energy levels they are now in the ________________ state.
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Once in the excited state the atoms are ______________ and thus _______ energy when they fall back down to their original energy levels. This process is called _______________.
This __________ of absorption and emission happens very fast over and over again.
Atoms can be excited using _________, light, or electricity.
Emission is usually in the form of __________. Different energies of light have different ___________. The light spectrum: (lower energy)ROYGBIV (higher energy)
This is actually how we see colors!
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