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Elements


An element is either classified as a
metal, nonmetal or metalloid.
The classification depends on the
elements location on the periodic
table.
Metals are in pink.
 Nonmetals are in lime green.
 Metalloids are in white.

B
Si
Ge As
Sb Te
Po At
Elements
1
2
3
4
5
6
7
 Metals
are
in yellow.
Elements
1
2
3
4
5
6
7
 Nonmetals
in purple.
are
Elements
1
2
3
4
5
6
7
 Metalloids
in green.
are
Properties of Metals
 Metals
are elements that have luster,
conduct heat and electricity, and
usually bend without breaking.
 Metals are also ductile (can be drawn
out into a wire).
Properties of Metals
 All
metals except mercury (Hg) are
solids at room temperature; in fact,
most have extremely high melting
points and high boiling points.
Properties of Metals
A
metal’s reactivity is its ability to
react with another substance.
 Metals in the first and second
column of the periodic table are more
reactive than other metals.
Properties of Nonmetals
 Although
the majority of the elements
in the periodic table are metals, many
nonmetals are abundant in nature.
Properties of Nonmetals
 Most
nonmetals don’t conduct
electricity, are much poorer
conductors of heat than metals, and
are brittle when solid.
 Many are gases at room temperature;
those that are solids lack the luster of
metals.
Properties of Nonmetals
 Their
melting points tend to be lower
than those of metals.
 Fluorine is the most reactive
nonmetal.
Properties of Metalloids
 Metalloids
have some chemical and
physical properties of metals and
other properties of nonmetals.
 In the periodic table, the metalloids
lie along the border between metals
and nonmetals.
Properties of Metalloids
Properties of Metalloids
 Some
metalloids such as silicon,
germanium (Ge), and arsenic (As) are
semiconductors.
 A semiconductor is an element that
does not conduct electricity as well
as a metal, but does conduct slightly
better than a nonmetal.
Objectives
 PSc.2.1.4
– Interpret the data presented in
the Bohr model diagrams and
dot diagrams for atoms and ions
of elements 1 through 18.
Modern View of the Atom
 The
atom has two regions and is
3-dimensional.
 The nucleus is at the center and
contains the protons and neutrons.
Modern View of the Atom
 The
electron
cloud is the
region where you
might find an
electron and most
of the volume of
an atom.
Subatomic Particles
Name
Symbol Charge
Relative
mass
Electron
e-
-1
1/2000
Proton
p+
+1
1
Neutron
n0
0
1
Atomic Number
 The
atomic number of an element is
the number of protons in the
nucleus of an atom of that element.
 The number of protons determines
identity of an element, as well as
many of its chemical and physical
properties.
Mass Number
 The
sum of the protons and
neutrons in the nucleus is the mass
number of that particular atom.
Symbols
 Elements
can be represented by using
the symbol of the element, the mass
number and the atomic number.
Mass
number
 The
Atomic
number
X
mass number is the atomic mass
rounded to a whole number.
Problem

Determine the following for the
fluorine atom depicted below.
a) number of protons (9)
19
9
c) number of electrons (9)
b) number of neutrons (10)
d) atomic number (9)
e) mass number
(19)
F
Problem

Determine the following for the
bromine atom depicted below.
a) number of protons (35)
b) number of neutrons (45) 80
c)
Br
35
number of electrons (35)
d) atomic number (35)
e) mass number
(80)
Problem

If an element has an atomic
number of 34 and a mass number
of 78 what is the
a) number of protons (34)
b) number of neutrons (44)
c) number of electrons (34)
d) complete symbol
78
34
Se
Problem

If an element has 91 protons and
140 neutrons what is the
a) atomic number (91)
b) mass number
(140)
c) number of electrons (91)
231
d) complete symbol
91
Pa
Cations
A
cation is a positive ion.
 It is formed when an atom loses one or
more electrons.
2+
Ca
Anions
 An
anion is a negative ion.
 It is formed when an atom gains one or
more electrons.
1Cl
Problem

Determine the following for the
chlorine ion depicted below.
a) number of neutrons (18)
b) number of electrons (18) 35
1Cl
17
c) number of protons (17)
d) mass number
(35)
e) atomic number (17)
Problem

Determine the following for the
aluminum ion depicted below.
a) mass number (27)
b) number of electrons (10) 27
c) atomic number (13)
d) number of protons (13)
e) number of neutrons (14)
3+
Al
13
Isotopes
 In
1910, J.J. Thomson discovered
that neon consisted of atoms of two
different masses.
Isotopes
 Atoms
of an element that are
chemically alike but differ in mass
are called isotopes of the element.
Isotopic Notation
 Consider
the isotope of carbon that
has a mass number of 14. The
following are different ways to write
symbols for this isotope.
Carbon-14
14C
C-14
14C
6
The Bohr Model of the Atom
 Niels
Bohr, a young Danish physicist
working in Rutherford’s laboratory in
1913, suggested that the single
electron in a hydrogen atom moves
around the nucleus in only certain
allowed circular orbits.
The Bohr Model of the Atom
 The
atom looked like a miniature
solar system.
 The nucleus is represented by the
sun, and the electrons act like the
planets.
The Bohr Model of the Atom
Nucleus
Electron
Orbit
Energy Levels
The Bohr Model of the Atom
 The
orbits are circular and are at
different levels.
 Amounts of energy separate one
level from another.
Bohr Diagrams
1)
2)
3)
Find your element on the periodic
table.
Determine the number of electrons
This is how many electrons you will
draw.
Bohr Diagrams
 Find
out which period
(row) your element is
in.
 Elements in the 1st
period have one energy
level.
 Elements in the 2nd
period have two energy
levels, and so on.
Bohr Diagrams
1)
C
2)
3)
Draw a nucleus with
the element symbol
inside.
Carbon is in the 2nd
period, so it has two
energy levels, or
shells.
Draw the shells around
the nucleus.
Bohr Diagrams
1)
C
2)
3)
Add the
electrons.
Carbon has 6
electrons.
The first shell
can only hold 2
electrons.
Bohr Diagrams
1)
C
2)
The second
shell can only
hold 8
electrons.
The third shell
can only hold
18 electrons.
Bohr Diagrams
1)
C
2)
3)
Since you have 2
electrons already
drawn, you need to
add 4 more.
These go in the 2nd
shell.
Add one at a time starting on the right
side and going
counter-clockwise.
Bohr Diagrams
Try the following
elements on your own:
a) H
b) He
c) O2d) Mg2+
e) Ne
f) Ar
Bohr Diagrams
H
Try the following
elements on your own:
a) H 1 electron
b) He
c) O2d) Mg2+
e) Ne
f) Ar
Bohr Diagrams
He
Try the following
elements on your own:
a) H
b) He 2 electrons
c) O2d) Mg2+
e) Ne
f) Ar
Bohr Diagrams
O2-
Try the following
elements on your own:
a) H
b) He
c) O2- 10 electrons
d) Mg2+
e) Ne
f) Ar
Bohr Diagrams
Mg2+
Try the following elements
on your own:
a) H
b) He
c) O2d) Mg2+ 10 electrons
e) Ne
f) Ar
Bohr Diagrams
Ne
Try the following
elements on your own:
a) H
b) He
c) O2d) Mg2+
e) Ne 10 electrons
f) Ar
Bohr Diagrams
Ar
Try the following
elements on your own:
a) H
b) He
c) O2d) Mg2+
e) Ne
f) Ar 18 electrons
Electron Dot Diagrams
♦ An electron dot diagram
illustrates valence electrons as
dots (or other small symbols)
around the chemical symbol of
an element.
Electron Dot Diagrams
♦ Each dot represents one
valence electron.
♦ In the dot diagram, the element’s
symbol represents the core of
the atom—the nucleus plus all
the inner electrons.
Electron Dot Diagrams
 Write
the
symbol.
♦ Put one dot for
each valence
electron.
♦ Don’t pair
electrons up until
you have to.
X
Electron Dot Diagrams
Electron Dot Diagrams
Write a Lewis dot diagram for
chlorine.
Electron Dot Diagrams
Write a Lewis dot diagram for
calcium.
Electron Dot Diagrams
Write a Lewis dot diagram for
potassium.
CHEMICAL BONDING and
CHEMICAL
INTERACTIONS
PSc.2.2 OBJECTIVE: Understand
chemical bonding and chemical
interactions.
Objectives

PSc.2.2.1
–Infer valence electrons,
oxidation number, and
reactivity of an element
based on its location on the
Periodic Table.
Bonding and Molecules
The outer
electrons are
involved in
bonding.
 These are called
valence
electrons.

Bonding and Molecules
Most stable
atoms have eight
valence electrons.
 When an atom
has 8 valence
electrons, it is
said to have an
octet of
electrons.

The Octet Rule
Oxidation Number

An oxidation
number
indicates how
many
electrons are
lost, gained, or
shared when
bonding
occurs.

1A
2A
The elements in the A groups
8A
0
are called the representative
3A 4A 5A 6A 7A
elements.
1A



Group 1A elements have one
valence electron.
They form 1+ ions after losing the
one valence electron.
1+ is referred to as the oxidation
number for Group 1A elements.

2A


Group 2A elements have two
valence electrons.
They form 2+ ions after losing the
2 valence electrons.
2+ is referred to as the oxidation
number for Group 2A elements.



Group 3A elements
have three valence
electrons.
They form 3+ ions after
losing the 3 valence
electrons.
3+ is referred to as the
oxidation number for
Group 3A elements.
3A



Group 4A elements
have four valence
electrons.
They form 4+ ions after
losing the 4 valence
electrons.
They could just as
easily form 4- ions
after gaining four
additional electrons.
4A

Group 4A elements
could have a 4+ or 4oxidation number,
depending on the
element with which
they are bonding.
4A
Group 4A
Two elements in Group 4A have
multiple oxidation numbers of 2+ and
4+.
 These two elements are tin (Sn) and
lead (Pb).




Group 5A elements
have five valence
electrons.
They form 3- ions after
gaining 3 additional
electrons.
3- is referred to as the
oxidation number for
Group 5A elements.
5A



Group 6A elements
have six valence
electrons.
They form 2- ions after
gaining 2 additional
electrons.
2- is referred to as the
oxidation number for
Group 6A elements.
6A



Group 7A elements
have seven valence
electrons.
They form 1- ions after
gaining 1 additional
electron.
1- is referred to as the
oxidation number for
Group 7A elements.
7A


Group 8A elements have eight
valence electrons, except
helium which only has 2.
Group 8A elements, with a full
complement of valence
electrons, are generally not
reactive.
8A
Question
How many valence electrons are in
an atom of each of the following
elements?
a) Magnesium (Mg) (2)
b) Selenium (Se) (6)
c) Tin (Sn) (4)
Question
Determine the oxidation number of
each of the following elements.
a) Potassium (K)
b) Chlorine (Cl)
c) Tin (IV) (Sn)
(1+)
(1-)
(4+)
Reactivity of Metals

In general, the reactivity of metals
increases from top to bottom and
decreases from left to right.
Reactivity of Metals
Reactivity of Nonmetals

In general, the reactivity of nonmetals
increases from left to right and
decreases from top to bottom.