Download Test 2 Review - Chemistry

Democritus
-400 B.C.
- Coined the term “atom”
Aristotle
-384-322 B.C.
- Believed matter is
continuous




All matter is composed of tiny particles
called atoms.
Atoms of the same element have the
same properties. (mass, size, etc.)
In a chemical reaction, matter cannot be
created or destroyed – Law of
Conservation of Mass
Compounds always contain elements in
the same ratio by mass – Law of Definite
Proportions
Dalton
1810


Showed electrons are negatively charged
Every atom’s electrons have same charge

Conclusion: most of an atom is empty space


Dalton’s Model (1803)

Rutherford’s Model (1909)

Thomson’s Model (1897)

Bohr’s Model (1913)
Electron-cloud
Model (present)

Nucleus
◦ Contains protons and neutrons
◦ Makes up most of an atom’s mass
◦ Is positively charged
 Proton (+ charge)
 Neutron (0 charge)

Electron Cloud
◦ Contains electrons
◦ Makes up most of an atom’s volume
Subatomic Charge Location
Particles
Mass
Other
Feature
Proton
+
Nucleus
1 amu
Defines the
element
-Atomic #
Neutron
0
Nucleus
1 amu
Change # to
form isotopes
Electron
-
Electron
Cloud
~0
Atom’s volume
-dictate’s
reactivity

Atoms of the same element that differ in
mass
◦ Atomic # = # protons
◦ # protons = # electrons
◦ Mass # = # protons + # neutrons
mass#
atomic#
X
108
47
Ag
207
82
80
35
Pb
Br
Silver - 108
Lead - 207
Bromine - 80

Arranged by increasing atomic #

Rows = Periods

Columns = Groups OR Families

The weighted average of its naturally
occurring isotopes.
Chemical Name
Atomic #
Chemical Symbol
Atomic Mass
(Average Atomic
Mass)
 Multiply
the mass of each isotope
by its abundance to get the
weighted average.
(%  mass)  (%  mass)  .....
100

Energy levels are a particular distance from
the nucleus
# e- =
2
8
18
32
50
n=
1
2
3
4
5

The maximum number of electrons in
each nrg level is 2n2
◦ At n = 1, there can be 2(1)2 = 2 e-
◦ At n = 2, there can be 2(2)2 = 8 e◦ At n = 3, there can be 2(3)2 = 18 e-


Tells the shape
Each nrg level has a # of sublevels = to n
Energy Level
(n)
# Sublevels
Sublevels
1
1
1s
2
2
2s, 2p
3
3
3s, 3p, 3d
4
4
4s, 4p, 4d, 4f


The 3rd quantum number (m) tells which
orbital and electron occupies.
One pair (2e-) of electrons can occupy each
orbital
◦ s sublevels have 1 orbital (2e-)
◦ p sublevels have 3 orbitals (6e-)
◦ d sublevels have 5 orbitals (10e-)
◦ f sublevels have 7 orbitals (14e-)

** each orbital can hold UP TO 2 e-**

Indicates direction of spin of e◦ -1/2 , +1/2

(clockwise, counterclockwise)
Pauli Exclusion Principle states that no two
electrons in an atom can have the same set of
4 quantum numbers.
◦ The two e- in an orbital must have opposite spins.

Helium has 2 electrons
◦
◦
◦
◦

n=1
l =s
m=1
s = 1 up, 1 down
Helium’s electron configuration would be:
Principle
Quantum #
1s
2
# of e-
Sublevel
1s
2s
3s
4s
5s
6s
7s
2p
3p
4p
5p
6p
7p
3d
4d
5d
6d
7d
4f
5f
6f
7f
-
Sublevels fill in order of increasing nrg
-
1s2s2p3s3p4s3d4p5s4d5p6s4f5d6p7s5f6d7p


e- first occupy the lowest possible nrg level
available.
Electron Dot Notation – show only valence e-,
those in the outer most nrg level
◦ ONLY UP TO 8e◦ 8 e- = stable

Valence electrons – e- in the highest nrg levels
◦ These e- are what form bonds

Examples:
H
He
Li
C
Be
Mg
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
What would the electron dot notation be for
titanium?
Ti = 22e- BUT only 2 valence eElectron Configuration Notation
2
2
6
2
6
2
1s 2s 2 p 3s 3 p 4s 3d

Electron Dot Notation
Ti
2
Valence e-
-d’s are NEVER valence e-, they
ALWAYS fill after a high nrg level
-Same for f’s



Show all orbitals with electrons
Electrons represented as up and down arrows
Arrows must be opposite within orbitals
Nitrogen (7)
1s
2s
2p
1s
2s
2p
Fluorine (9)

Lose or gain e◦ Anions – are negatively charged, having gained e◦ Cations – are positively charged, having lost e-
** atoms will gain or lose e- to become more stable**

1s
Filled and half-filled sublevels are more
stable than partially filled sublevels.
2s


2p
3s
3p
4s
3d
This Cr takes an e- from 4s to put one e- in
each of its 3d orbitals and Cu takes a 4s to fill
each of its 3d orbitals
Orbitals are stable when either full or half-full


e- at higher nrg states are not stable
These e- want to return to their ground state
to become stable
◦ Lowest possible nrg level

Distance between nrg levels is NOT all the
same.
R O Y G B I V

Blue light has a higher frequency than red.

Light of a particular wavelength (λ) has a
particular frequency (ν) and nrg (E).
E  h 


c

If ν, λ or E are known, the other 2 can be
calculated.
m
c  3.00 10
s
8
h  6.63 10
34
speed of light
J s
Planck’s constant


What do the following symbols stand for?
What are their units?
1
1
ν
Frequency
Hz  s 

λ
Wavelength

h
Planck’s Constant

c
Speed of Light

E
Energy
s
m, nm
J s
m
s
J

Why each element produces a unique line
spectra.

The properties of the elements are a periodic
function of their atomic masses
◦ periodic means repeating, like the moon cycle,
every month it repeats

**atomic number was not known during
Mendeleev’s time


The properties of the elements are a periodic
function of their atomic numbers
Using x-rays, Henry Moseley determined the
number of protons per element
◦ This is Atomic Number

Elements with similar e- configurations are in
the same columns known as “groups” or
“families”
◦ Families  familiar characteristics
◦ Families have the same number of v.e.’s

Rows are periods, each row designates a
different nrg level
Columns are groups or families and contain

Notable rows and columns

elements with similar properties
◦ Rows:
 4f – Lanthanides
 5f - Actinides
◦ Columns:




1 or IA – Alkali Metals
2 or IIA – Alkaline Earth Metals
17 or VIIA – Halogens
18 or VIIIA – Noble gases

“A” Groups

Filling the ‘s’ and ‘p’ sublevels

Contains both metals and non metals

“B” Groups

Fills the ‘d’ sublevels

Made up of only metals
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Fill the ‘f’ sublevels
Lanthanides
Actinides
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INCREASES as you go DOWN a group because
of nrg levels
DECREASES as you go ACROSS a group
because of nuclear charge
Noble gases radii are found to be larger
because they don’t interact with other atoms
of the same element as most others do.

Atoms can lose or gain e- to complete or
empty an outer nrg level
◦ Every atom wants an octet


Ion – an atom that has a + or – charge
Metals
◦ Lose e- giving them a + charge
◦ Decreases their radius
◦ These are cations

Nonmetals
◦ Gain e- giving them a – charge
◦ Increases their radius
◦ These are anions

Nrg needed to remove an e- from an atom
◦ Unit = (kJ/mol)

ACROSS a period, it INCREASES
◦ Due to increase in nuclear charge

DOWN a group, it DECREASES
◦ Due to increased atomic radius and shielding effect


Metals = low I.E.
Nonmetals = high I.E. (especially noble gases)

The power of an atom in a molecule to
ATTRACT e- to itself
◦
◦
◦
◦

Ability to “hold on to e- more”
DECREASES from top to bottom of group
INCREASES from left to right in periods
F has the highest E.N.
High E.N.’s gain e- and form (-) ions
◦ The more stable an atom, the less likely it will
attract an e Would result in (-)E.N.

High E.N. = High electron affinity