Unit 2 .pptxbbbbbbbbbbbbbbbbbbbbbbbbbbbbb

What is an Atom?
- Atoms are often referred to as the building blocks of
matter.
- Each element on the periodic table is composed of
one type of atom and cannot be broken down into a
simpler substance (why?)
- Living things consist of atoms of different elements (Give
Examples)
https://www.youtube.com/watch?v=ajg07Dnc1BQ

Living things consist of atoms of
different elements

 Atoms consists of three smaller particles:
protons, neutrons and electrons
 Protons and neutrons form the dense center with
the most mass of an atom called the Nucleus
 Electrons are much smaller particles outside of
the nucleus
 Protons are positively charged
Electrons are negatively charged
Neutrons are neutral
Since atom has equal numbers of positively
charged protons and negatively charged
electrons, it is electrically neutral
 Explain why is an atom electrically neutral?
Structure of an Atom

Atoms have neutral charge.....
Number of
electrons
Number
of
protons
e- p

Structure of an Atom
- Inner Structure : Nucleus which consists of the
positive protons and Neutral neutrons
(Mass of an atom )
- Outer Structure: Electron cloud - an area around
the nucleus where electrons are likely to be found
orbiting the nucleus in several energy levels.

Electrons follow a specific order to fill the energy
levels
Maximum
of 2
electrons
Nucleus
Maximum
of 8
electrons Maximum
of 8
electrons*
*Applies to the first
18 elements only

Properties of sub-atomic particles
Atomic particle Proton (p+) Neutron (n) Electron (e-)
Relative Mass 1 1 1/1836
Relative charge +1 0 -1
Description positively charged
particles with a
relative atomic
mass of 1.
have no charge but
have a mass of
negatively charged
particles with
negligible mass

Atomic Mass
Mass
of
neutrons
Mass
of
protons
Mass
of
Atom
Mass of electrons are almost equal to zero and are not counted
to the mass of an atom!
Atom Characteristics

Atomic Number
Number
of
Electrons
Number
of
protons
Atomic
Number
Atom Characteristics

Decoding Atom Information
from the Periodic Table
C
Carbon
6
12.0
Atom’s
Symbol
Atom’s
Name
Atomic
Number
Atomic
Mass

Decoding Atom Information
from the Periodic Table
Carbon
12.0
Atomic number
# of protons = # of
electrons
Atomic mass = # of
protons plus the # of
neutrons
6
C
Then,
- Number of Protons = 6
-Number of electrons = 6
-Number of Neutrons = 6

Decode this Atom
Information
Atomic Number
Mass Number
Numbers of P,e and n. (Subatom)

1. Live Worksheet:
https://www.liveworksheets.com/w/en/science/2181023
2. Pick an Element from the periodic table and
Decode it’s atomic structure..

Elements, Mixtures &
Compounds
https://www.youtube.com/watch?v=DZ6Ap8Zyb9w
- Observe the differences between the Element/
Molecule, compound & Mixture.
* Definition
* Separation
* Examples

Substances can be classified as elements
or compounds.
• A compound is a substance that contains
two or more elements chemically combined
in a fixed proportion.
• Chemically combined makes it difficult to
separate.
Distinguishing Elements
and Compounds

Elements and Compounds
 Element:
-one type of atom
-Cannot be broken down into a
simpler substance by ordinary
chemical means
 Compound:
-is a substance made of atoms of
different elements bonded together
in a certain ratio
-Its properties are different from
the properties of the elements that
make up the compound

There is a key difference between elements
and compounds.
• Compounds can be broken down into
simpler substances by chemical
means, but elements cannot.
Distinguishing Elements
and Compounds

Classification of Matter
• A mixture is a blend of two or more kinds of matter,
each of which retains its own identity and properties.
• mixed together physically
• can usually be separated
• Homogeneous mixtures are called solutions
• uniform in composition (salt-water solution)
• Heterogeneous mixtures
• not uniform throughout (clay-water mixture)

No matter what you do to a silvery
liquid, it doesn’t seem to change. Is it
more likely to be a substance or a
mixture?

No matter what you do to a silvery
liquid, it doesn’t seem to change. Is it
more likely to be a substance or a
mixture?
It is most likely a substance. If it was a
mixture, it would likely have separated
when manipulated chemically or physically.

https://quizizz.com/admin/quiz/5b8b47427dedb1001ac
6d60f/element-compound-mixture?fromSearch=true&
source=
- Now You Draw Element, Compound & Mixtures
(Homogenous & Heterogenous) - simple figures and
give examples on each

Symbols and Formulas
What do chemists use to represent
elements and compounds?
Chemists use chemical symbols to
represent elements, and chemical
formulas to represent compounds.

Symbols and Latin Names for Some Elements
Name Symbol Latin name
Sodium Na natrium
Potassium K kalium
Antimony Sb stibium
Copper Cu cuprum
Gold Au aurum
Silver Ag argentum
Iron Fe ferrum
Lead Pb plumbum
Tin Sn stannum
Interpret Data

Chemical symbols provide a shorthand way
to write the chemical formulas of
compounds.
• The symbols for hydrogen, oxygen, and
carbon are H, O, and C.
• The formula for water is H2O.
• The formula for sucrose, or table sugar, is
C12H22O11.

Subscripts in the chemical formulas tell you
how many of each type of element are in
the compound.
• The subscript 2 in H2O indicates that there
are always two parts of hydrogen for each
part of oxygen in water.
• Because a compound has a fixed
composition, the formula for a compound is
always the same.

Chemical symbols are abbreviations
for the names of elements in what
language?
Chemical symbols are abbreviations for
the names of elements in Latin.

Bohr - electron orbits
Niels Bohr Limitations of the Rutherford model
Electrons will lose energy if
circulating continuously and fall
into the nucleus
Electrons emit light (photons) only
when they are given a certain
finite amount of energy. This
should happen at any level
of energy.

Bohr Model of the Atom
The electrons can only travel in
special orbits: at a certain
discrete set of distances from the
nucleus with specific energies.
The electrons do not
continuously lose energy as they
travel. They can only gain and
lose energy by jumping from one
allowed orbit to another

Bohr Model
 Bohr determined that
electrons circled in a
 definite path around the
nucleus
 This path was known as an
orbit or shell

What is electron configuration?
 Electron configuration Is the
arrangement of electrons in an
atom, molecule or other body.

Filling Electron orbits
• The first orbit would contain a
maximum of 2 electrons
• The second orbit would have a
maximum of 8 electrons
• The third orbit could
have a maximum of 8
electrons.
2 e-
8 e-
1 e-
11 e-
Let’s assume an unknown
element X had 11 electrons

Bohr- Rutherford diagrams
Bohr-Rutherford diagrams
11 p
10 n
37
How to draw one
Since there are 3 shells or
orbits, we draw three circles
each one bigger than the
next
Each electron is denoted by an
X.
Draw in the number of
electrons corresponding
to
each orbital or shell
2,8,1

Bohr- Rutherford diagrams
Bohr-Rutherford diagrams
11 p
10 n
How to draw one
n = 10 and since e- = p, p = 15
Write out electron
configuration
2,8,5
to
2,8,5

Bohr- Rutherford diagram
Bohr-Rutherford diagram
15 p
7 n
How to draw
Since Z = 10, p = 15
Since n = A – Z = 17 – 10 = 7
Since e- = p, there are
10 e-
Write out electron
configuration
2,8
to
2,8

Mention the difference
Different Atomic Masses because they have different Numbers of Neutrons
Electrons = 6
Protons = 6
Neutrons = 6
Electrons = 6
Protons = 6
Neutrons = 7
https://www.youtube.com/watch?v=xjY5p-
1CDr8

Isotopes
Elements may have atoms that have different numbers of neutrons.
Chemically, they are the same - they have the same number of
electrons and protons.
But because neutrons influence atomic mass, if atoms have
different numbers of neutrons, then they will have different
atomic masses.
These atoms are known as isotopes.

Are those Isotopes ?
Why? Present the differences .

Formation of an ion
 Ion: is an atom that has gained or lost one or more
electrons
 It is formed because an atom is more stable when its
outermost energy level is full
 This charge gives ions certain properties as ionic
compounds easily dissolve in water
 Ions play large roles in organisms ?

Elements and symbols
Element Symbol Atomic
Number (Z)
Electronic
configuration
Hydrogen H 1 1
Helium He 2 2
Lithium Li 3 2,1
Beryllium Be 4 2,2
Boron B 5 2,3
Carbon C 6 2,4
Nitrogen N 7 2,5
Oxygen O 8 2,6
Fluorine F 9 2,7
Neon Ne 10 2,8

Elements and symbols
Atoms and The Periodic Table Prepared by JGL
Element Symbol Atomic
Number (Z)
Electronic configuration
Sodium Na 11 2,8,1
Magnesium Mg 12 2,8,2
Aluminium Al 13 2,8,3
Silicon Si 14 2,8,4
Phosphorus P 15 2,8,5
Sulphur S 16 2,8,6
Chlorine Cl 17 2,8,7
Argon Ar 18 2,8,8
Potassium K 19 2,8,8,1
Calcium Ca 20 2,8,8,2

The Periodic Table—A Preview
Why is a periodic table useful?
1. All the known elements are organized in
a special table called the periodic table.
• A periodic table is an arrangement of
elements in which the elements are
separated into groups based on a set of
repeating properties.

2. The periodic table allows you to
easily compare the properties of one
element (or a group of elements) to
another element (or group of
elements).
The Periodic Table—A
Preview

Preview
Each element is identified by its symbol
placed in a square.

How is the periodic table arranged?
- Number of Rows
- Number of columns
- What make some elements share the
similar chemistry?
The Periodic Table
—A Video
https://www.youtube.com/watch?v=j7JcyDBHCBc

What is the Periodic Table?
A tabular arrangement of the elements according to their
atomic numbers so that elements with similar properties
are in the same column.
This is an easy reference chart for chemists to use to
interpret the properties of groups of elements, rather
than try to memorize all the properties of each element

Each element is identified by its symbol
placed in a square.
• The elements are listed in order from left to
right and top to bottom by atomic number, a
number that is unique to each element.
• The atomic number of the element is shown
centered above the symbol.
Preview
– Hydrogen (H), the lightest element, is in the top left
corner.
– Helium (He), atomic number 2, is at the top right.
– Lithium, atomic number 3, is at the left end of the
second row.

Each horizontal row of the periodic table
is called a period.
• There are seven periods in the periodic
table.
• The number of elements per period ranges
from 2 (hydrogen and helium) in Period 1
to 32 in Period 6.
Preview

Within a period, the properties of the
elements vary as you move across the
period.
• This pattern of properties then repeats as
you move to the next period.
Preview

Each vertical column of the periodic table
is called a group, or family.
• Elements within a group have similar
chemical and physical properties.
• Note that each group is identified by a
number and the letter A or B.
– Group 2A contains the elements
beryllium (Be), magnesium (Mg), calcium
(Ca), strontium (Sr), barium (Ba), and
radium (Ra).
Preview

Dmitri Mendeleev
time and their properties
predicted
Produced a table based on
atomic mass but arranged
'periodically' with elements
with similar properties under
each other.
Gaps were left for elements
that were unknown at that
Mendeleev's Periodic Table was
import
ant
be
ca
us
e it
properties of elements to be predicted
by means of the 'periodic law':
properties of the elements vary
periodically with their atomic weights.

Henry Moseley
Determined the atomic
number of each of the
elements
He modified the 'Periodic
Law' to read that the
properties of the elements
vary periodically with their
atomic numbers.

Groups in the periodic table
These columns are known as
GROUPS
4 5 6 7 8 9
10 11 12 13 14 15 16 17 18
1 2 3
There are
18
GROUPS
GROUPS are also known as
FAMILIES

Main periods in periodic table
1
2
3
4
5
6
7
The rows are known as PERIODS. There are 7 periods

The periodic table
Elements within a group have similar
physical and chemical properties
All have the same number of
electrons in their outermost or
valence shells
Example Na
(2,8,1) and
K (2,8,8,1)
are both in
Group 1

The periodic table
Elements within a period have
increasingly similar or dissimilar
properties
The period number corresponds
to the number of shells
Example Na
(2,8,1) and
Mg(2,8,2)
have 3shells
and are in
Period 3

Metals and Non-metals
14 15 16 17 18
10 11 12 13
1 2 3 4 5 6 7 8 9
Group 1 to 13 and periods 8 and 9 are
METAL
S
Metals
Metals
Groups 14 to 18 are Non-metals
Non-
Metals

Groups
i
n the period
4 5 6 7 8 9
10 11 12 13 14 15 16 17 18
1 2 3
Some GROUPS and PERIODS have
other common na es
ic table
Group 1 metals are
known as the
ALKALI metals
Group 2 metals are known
as the ALKALINE earth
METALS
Groups 3 to 12 are
known as the
TRANSITION metals
m
Group 1
known
a
HALOG
7 is
s the
ENS
The elements
touching this
staircase are
known as the
METTALOID
S
18 is
as the
Group
known
NOBLE
GASES
as the
LANTHANIDE
metals
Period 8 is known
8 Period 9 is known as
the ACTINIDE
metals
9
Atoms and The Periodic Table Prepared by JGL 8/1/2009
63

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