Transcript No Slide Title

Elements
Elements are
 pure substances that cannot be separated into
simpler substances by ordinary laboratory
processes
 the building blocks of matter
gold
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carbon
aluminum
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Symbols of Elements
A symbol
 represents the name of an element
 consists of 1 or 2 letters
 starts with a capital letter
Examples:
1-Letter Symbols
C carbon
N nitrogen
F
fluorine
O oxygen
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2-Letter Symbols
Co
cobalt
Ca
calcium
Al
aluminum
Mg
magnesium
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Groups and Periods (continued)
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Representative Elements
 Several groups of representative elements are
known by common names.
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Metals, Nonmetals, and Metalloids
The heavy zigzag line
separates metals and
nonmetals.
 Metals are located to
the left.
 Nonmetals are located
to the right.
 Metalloids are located
along the heavy zigzag
line between the metals
and nonmetals.
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Properties of Metals, Nonmetals,
and Metalloids
Metals
 are shiny and ductile
 are good conductors of heat and electricity
Nonmetals
 are dull, brittle, and poor conductors of heat and
electricity
 are good insulators
Metalloids
 are better conductors than nonmetals, but not as
good as metals
 are used as semiconductors and insulators
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Subatomic Particles
Atoms contain subatomic particles.
 Protons have a positive (+) charge.
 Electrons have a negative (–) charge.
 Like charges repel, and unlike
charges attract.
 Neutrons are neutral.
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Atomic Number
The atomic number
 is specific for each element
 is the same for all atoms of an element
 is equal to the number of protons in an atom
 appears above the symbol of an element
Atomic Number
Symbol
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Na
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Number of Electrons in an Atom
An atom
 of an element is electrically neutral; the net charge
of an atom is zero
 has an equal number of protons and electrons.
number of protons = number of electrons
 of aluminum has 13 protons and 13 electrons; the
net charge is zero
13 protons (13+) + 13 electrons (13–) = 0
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Mass Number
The mass number
 represents the number of particles in the nucleus.
 is equal to the
number of protons + number of neutrons
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Isotopes
Isotopes
 are atoms of the same element that have different
mass numbers
 have the same number of protons but different
numbers of neutrons
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Nuclear Symbol
A nuclear symbol
 represents a particular atom of an element
 gives the mass number in the upper left corner and
the atomic number in the lower left corner
Example: An atom of sodium with atomic number
11 and a mass number 23 has the following atomic
symbol:
23
mass number
11
atomic number
Na
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Nuclear Symbols
For an atom, the nuclear symbol gives the number of
 protons (p+)
 neutrons (n)
 electrons (e–)
16
8
O
8 p+
8n
8 e–
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31
15
P
15 p+
16 n
15 e–
65
30
Zn
30 p+
35 n
30 e–
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Isotopes of Sulfur
A sample of naturally
occurring sulfur contains
several isotopes with the
following abundances:
Isotope % Abundance
32
95.02
16 S
33
16
S
0.75
34
16
S
4.21
36
16
S
0.02
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16
S
33
16
S
34
16
S
36
16
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S
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Electromagnetic Radiation
Electromagnetic radiation
 is energy that travels as waves through space
 is described in terms of wavelength and
frequency
 moves at the speed of light in a vacuum
speed of light = 3.0 x 108 m/s
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Electromagnetic Spectrum
The electromagnetic spectrum
 arranges forms of energy from lowest to highest
 arranges energy from longest to shortest wavelengths
 shows visible light with wavelengths from 700–400 nm
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Example of Atomic Spectra
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Electron Energy Levels
Electrons are arranged in
specific energy levels that
 are labeled n = 1, n = 2,
n = 3, and so on
 increase in energy as n
increases
 have the electrons with the
lowest energy in the first
energy level (n = 1) closest
to the nucleus
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Energy Level Changes
 An electron absorbs
energy to “jump” to a
higher energy level.
 When an electron falls to
a lower energy level,
energy is emitted.
 In the visible range, the
emitted energy appears
as a color.
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Sublevels
Sublevels
 contain electrons with the same energy
 are found within each energy level.
 are designated by the letters s, p, d, and f
The number of sublevels is equal to the value of the
principal quantum number (n).
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Number of Sublevels
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Energy of Sublevels
In any energy level
 the s sublevel has the lowest energy
 the s sublevel is followed by the p, d, and f sublevels
(in order of increasing energy)
 higher sublevels are possible, but only s, p, d, and f
sublevels are needed to hold the electrons in the
atoms known today
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Orbitals
An orbital
 is a three-dimensional space
around a nucleus where an
electron is most likely to be found
 has a shape that represents
electron density (not a path the
electron follows)
 can hold up to 2 electrons
 contains two electrons that must
spin in opposite
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s Orbitals
An s orbital
 has a spherical shape
around the nucleus
 increases in size around the
nucleus as the energy level
n value increases
 is a single orbital found in
each s sublevel
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p Orbitals
A p orbital
 has a two-lobed shape
 is one of three p orbitals that make up each p
sublevel
 increases in size as the value of n increases
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Sublevels and Orbitals
Each sublevel consists of a specific number of
orbitals.
 An s sublevel contains one s orbital.
 A p sublevel contains three p orbitals.
 A d sublevel contains five d orbitals.
 An f sublevel contains seven f orbitals.
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Electron configuration is how the electrons are
distributed among the various atomic orbitals in an
atom.
number of electrons
in the orbital or subshell
1s1
principal quantum
number n
angular momentum
quantum number l
Orbital diagram
H
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1s1
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7.8
Order of orbitals (filling) in multi-electron atom
1sGeneral,
< 2s
<and2p
< 3s
< 3p < 4s < 3d < 4p <Copyright
5s ©<20104d
< Education,
5p <Inc.6s
Organic,
Biological
Chemistry
Pearson
7.7
Orbital Diagrams
An orbital diagram shows
 orbitals as boxes in each sublevel
 electrons in orbitals as vertical arrows
 electrons in the same orbital with opposite spins (up
and down vertical arrows)
Example:
Orbital diagram for Li
1s2
2s1
filled half-filled
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2p
empty
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Electron Configuration
An electron configuration
 lists the sublevels filling with electrons in order of
increasing energy
 uses superscripts to show the number of electrons
in each sublevel
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“Fill up” electrons in lowest energy orbitals (Aufbau principle)
??
Be
Li
B5
C
3
64electrons
electrons
22s
222s
22p
12 1
BBe
Li1s1s
1s
2s
H
He12electron
electrons
He
H 1s
1s12
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7.9
Abbreviated Configurations
An abbreviated configuration shows
 the symbol of the noble gas in brackets that
represents completed sublevels
 the remaining electrons in order of their sublevels
Example: Chlorine has a configuration of
1s22s22p63s23p5
[Ne]
The abbreviated configuration for chlorine is
[Ne]3s23p5
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Sublevel Blocks
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Learning Check
Using the periodic table, give the atomic mass of
each element.
A. calcium
__________
B. aluminum
__________
C. lead
__________
D. barium
__________
E. iron
__________
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Solution
Using the periodic table, give the atomic mass of
each element.
A. calcium
40.08 amu
B. aluminum
26.98 amu
C. lead
207.2 amu
D. barium
137.3 amu
E. iron
55.85 amu
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Learning Check
1. Which of the following has the shortest wavelength?
A. microwaves B. blue light
C. UV light
2. Which of the following has the lowest energy?
A. red light
B. blue light
C. green light
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Solution
1. Which of the following has the shortest wavelength?
C. UV light
2. Which of the following has the lowest energy?
A. red light
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Learning Check
In each of the following energy level changes, indicate
if energy is 1) absorbed, 2) emitted, or 3) not changed.
A. An electron moves from the first energy level (n = 1)
to the third energy level (n = 3).
B. An electron falls from the third energy level to the
second energy level.
C. An electron moves within the third energy level.
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Solution
In each of the following energy level changes, indicate
if energy is 1) absorbed, 2) emitted, or 3) not changed.
A. An electron in an atom moves from the first energy
level (n = 1) to the third energy level (n = 3).
1) absorbed
B. An electron falls from the third energy level to the
second energy level.
2) emitted
C. An electron moves within the third energy level.
3) not changed
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Valence Electrons
The valence electrons
 determine the chemical properties of the elements
 are the electrons in the outermost, highest energy
level
 are related to the Group number of the element
Example: Phosphorus has 5 valence electrons.
5 valence
electrons
P Group 5A(15)
1s22s22p63s23p3
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Groups and Valence Electrons
All the elements in a group have the same number of
valence electrons.
Example: Elements in Group 2A(2) have two (2)
valence electrons.
Be
1s22s2
Mg
1s22s22p63s2
Ca
[Ar]4s2
Sr
[Kr]5s2
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Electron-Dot Symbols
An electron-dot symbol
 indicates valence electrons
as dots around the symbol of
the element
 of Mg shows two valence
electrons as single dots on the
sides of the symbol Mg
· Mg ·
·
or Mg · or
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·
· Mg
or
· Mg
·
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Writing Electron-Dot Symbols
The electron-dot symbols for
 Groups 1A(1) to 4A(14) use single dots
Na ·
· Mg ·
·
· Al ·
·
· C·
·
 Groups 5A(15) to 7A(17) use pairs and single dots.
··
· P·
·
··
:O·
·
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Groups and Electron-Dot Symbols
 in a group, all the electron-dot symbols have the
same number of valence electrons (dots).
Example: Atoms of elements in Group 2A(2) each
have 2 valence electrons.
2A(2)
· Be ·
· Mg ·
· Ca ·
· Sr ·
· Ba ·
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Atomic Size
Atomic size
 is described using the atomic radius
 is the distance from the nucleus to the valence
electrons
 increases going down a group
 decreases going across a period from left to right
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Atomic Size (continued)
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Atomic Radius Within A Group
Atomic radius
 increases going
down a group
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8.3
Ionization Energy
Ionization energy
 is the energy it takes to remove a valence electron
from an atom in the gaseous state
Na(g) + Energy (ionization)
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Na+(g) + e–
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General Trend in First Ionization Energies
Increasing First Ionization Energy
Increasing First Ionization Energy
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8.4
Learning Check
Write the orbital diagrams for
A. nitrogen
B. oxygen
C. magnesium
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Solution
Write the orbital diagrams for
A. nitrogen
1s
2s
2p
1s
2s
2p
1s
2s
2p
B. oxygen
C. magnesium
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3s
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Learning Check
Write the electron configuration and abbreviated
configuration for each of the following elements:
A. Cl
B. S
C. K
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Solution
A. Cl
1s22s22p63s23p5
[Ne]3s23p5
B. S
1s22s22p63s23p4
[Ne]3s23p4
C. K
1s22s22p63s23p64s1
[Ar]4s1
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Learning Check
Give the symbol of the element that has
A. the abbreviated configuration [Ar]4s23d6
B. four 3p electrons
C. two electrons in the 4d sublevel
D. the electron configuration
1s22s22p63s23p64s23d2
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Learning Check
State the number of valence electrons for each.
A. O
1) 4
2) 6
3) 8
B. Al
1) 13
2) 3
3) 1
C. Cl
1) 2
2) 5
3) 7
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Solution
State the number of valence electrons for each.
A. O
2) 6
B. Al
2) 3
C. Cl
3) 7
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