Download Atoms

S.MORRIS 2006

http://www.youtube.com/watch?v=uZ6zR
0vu7cU&feature=related
Bill Nye the Science Guy
The word atom is derived from the
Greek word atom which means
indivisible. (uncuttable)
 The Greeks concluded that matter
could be broken down into particles
too small to be seen.
 These particles were called atoms

The Atom
Atoms are made up of 3 types of particles
electrons , protons and neutrons .
 Electrons are tiny, very light particles
that have a negative electrical charge (-).
 Protons are much larger and have a
positive charge (+).
 Neutrons are large and heavy like
protons, however neutrons have no
electrical charge. (Neutral)

The Atom
ATOMIC STRUCTURE
He
2
4
Atomic number
the number of protons in an atom
Atomic mass
the number of protons and
neutrons in an atom
number of electrons = number of protons

Atomic mass = protons + neutrons

Atomic number = the number of protons

The number of protons = The number of
electrons.
The Atom




Give the symbol and number of
protons in one atom of:
Li, 3
Lithium __________________
Br, 35
Bromine __________________
Iron
__________________
Fe, 26
Cu, 29
Copper __________________
Checking on the Atom




Give the symbol and number of
electrons in a neutral atom of:
Uranium
__________________
U, 92
Cl, 17
Chlorine
__________________
B, 5
Boron
__________________
I, 53
Iodine
__________________
Checking on the Atom




Give the symbol and number of
neutrons in a neutral atom of:
Carbon
__________________
C, 12 - 6 = 6 neutrons
Cu, 64 - 29 = 35 neutrons
Copper
__________________
Fluorine
__________________
F, 19 - 9 = 10 neutrons
Mg, 24 - 12 = 12 neutrons
Magnesium __________________
Atomic mass = protons + neutrons
Checking on the Atom
1913
Niels Bohr
Bohr claimed electrons
move in paths around the
nucleus. They are very small
without much mass.
History of the Atom


Model of the atom pictures the electrons
moving around the nucleus in a region called
an electron cloud.
The electron cloud is a cloud of varying
density surrounding the nucleus. The varying
density shows where an electron is more or
less likely to be. Atoms with electrons in
higher energy levels have additional electron
clouds of different shapes that also show
where those electrons are likely to be.
What is the Electron Cloud
Model?
http://regentsprep.org/Regents/physics/phys05/catomodel/cloud.htm
Do you know
what these are
called?
Electron Orbital
What is the Electron Cloud Model?
Electrons can spin in any direction;
scientists cannot tell exactly where an
electron is at a given moment or where it
is going.
 They can calculate the probability that an
electron will be found in a given space.
This is quantum mechanics.
 The distance from the nucleus that the
electron spins is called its energy shell,
energy level, or orbital.

Orbital
Electrons are arranged in Energy Levels or
shells around the nucleus of an atom.
The first shell can hold
The second shell can hold
The third shell can hold
The fourth level can hold
The fifth level can hold
The sixth level can hold
The seventh level can hold
Atomic Structure
2 electrons
8 electrons
8 electrons
18 electrons
32 electrons
50 electrons
72 electrons
ELECTRONIC CONFIGURATION
With electronic configuration elements are represented
numerically by the number of electrons in their shells
and number of shells. For example;
Nitrogen
2 in 1st shell
5 in
2nd
shell
configuration = 2 , 5
2
+
5 = 7
N
7
14
ELECTRONIC CONFIGURATION
Write the electronic configuration for the following
elements;
a)
Ca
20
b)
Na
40
2,8,8,2
d)
Cl
17
35
2,8,7
11
23
c)
2,8,1
e)
Si
14
28
2,8,4
O
8
16
2,6
f)
B
5
11
2,3
DOT &
CROSS
DIAGRAMS
X
X X
N
X X
X X
N
7
14
Nitrogen
With Dot & Cross diagrams elements and compounds
are represented by Dots or Crosses to show electrons,
and circles to show the shells.
Dot and Cross Diagrams
Draw the Dot & Cross diagrams for the following
elements;
X
8
17
X
a) O
b)
Cl 35 X
16
X
X
X
X
X
X
X X X Cl X X
X
X
X
O
X
X
X
X
X
X
X
X
X
SUMMARY
1. The Atomic Number of an atom = number of
protons in the nucleus.
2. The Atomic Mass of an atom = number of
Protons + Neutrons in the nucleus.
3.
The number of Protons = Number of Electrons.
4.
Electrons orbit the nucleus in shells.
5.
Each shell can only carry a set number of electrons.
Elements
 Compounds
 Mixtures

Composition of Matter

Elements: Made of only one type of
atom. All atoms are identical.
◦ Atom: building block of an element
- Molecule: two or more atoms chemically
bonded together.
Examples: oxygen, nitrogen, iron
Composition of Matter

Compounds: made from atoms of two or
more elements that are chemically
combined.
◦ Examples: water (H2O), table salt(NaCl)

Mixtures: made up
of two or more
substances that are
not chemically
combined. Easily
separated.

◦ Examples: soil,
ocean water, air

Homogeneous
mixture: means that
mixture is evenly
spread out, and no
differences can be
detected. Ex: water,
vinegar
Heterogeneous
mixture: means that
material in mixture is
not evenly spread out
and differences can be
detected. Ex:soil,
chocolate chip cookie
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