# Atomic Structure and The Periodic Table (1)

```ATOMS
• Starter: I have in front of me a beaker of
water that has had sand mixed in and salt
dissolved in. Using the techniques we
learnt last lesson write a step by step guide
to separating out the salt and sand.
• Homework: Complete sheets on atomic
structure of the first 20 elements.
ATOMS
• All atoms (except Hydrogen)
of particles. They are:
• Protons – Positively charged
particle
• Neutrons – A neutral
(no
charge) particle
• Electrons – Negatively
charged particle
STRUCTURE OF THE ATOM
• Protons and neutrons are
located in the nucleus
• The electrons are located in
the shells/orbits.
Charge Mass Location
Proton
+1
Neutron neutral
Electron
-1
1
1
0
Nucleus
Nucleus
Shells
MASS AND ATOMIC NUMBERS
• Mass number – Total number
of protons and neutrons in
the nucleus.
• Atomic number – Number of
protons or electrons in the
atom.
• Number of neutrons =
• Mass number – Atomic
number
• How many protons, electrons
and neutrons does Lithium
have?
Example
9
Be
has
4
…protons,
…electrons
and …-…=… neutrons
Protons = atomic number
Electrons = atomic number
Neutrons = mass – atomic number
7
3Li
has …protons, …electrons
and …-…=… neutrons
19
9F
has …protons, …electrons
and …-…=… neutrons
27
13Al
has …protons, …electrons
and …-…=… neutrons
What is the mass of an atom with
? 10protons, 10 neutrons and 10 electrons?
? 8protons, 8 neutrons and 8 electrons?
? 9protons, 10 neutrons and 9 electrons?
? 18protons, 22 neutrons and 18 electrons?
• What can you tell me about the structure
of aluminium's atoms from how it’s
represented on the periodic table?
• Using the periodic table in your books
write down the element with the atomic
number 15
• An atom from element “E” is represented
as follows. What information can you give
tables!
Isotopes
• Lo1: To understand the terms
Isotope and relative atomic
mass
• Lo2: To learn how to draw the
electronic structure
of elements
STARTER
• A) How many protons,
neutrons and electrons
does this element have?
• B) Use your
to find out
atomic mass
with atomic
periodic table
the name and
of the element
number 92
• C) Identify the element I
have drawn on the board
197.0
79
SO IF ATOMIC MASS
IS THE NUMBER OF
PROTONS+ NEUTRONS
What’s going on
with Chlorine?
17 Protons
18
Neutrons
17
Electrons
17 Protons
20
Neutrons
17
Electrons
CHLORINE CAN EXIST IN TWO FORMS
Isotope: Atoms of an element with
different numbers of neutrons.
Isotopes have the same atomic number
but different atomic mass numbers.
Isotopes of an element have
identical chemical properties (They
behave the same way)
Carbon has two
isotopes
C
12
and
14
C6
6
What is the difference?
RELATIVE ATOMIC MASS
• We measure the weight of elements
in Atomic mass units (amu). The
scale of atomic mass units is so
that hydrogen, the lightest element
has an amu of 1.
• “The Relative Atomic Mass (Ar) of
an element is the mass of an
"average atom” taking into account
different isotopes of the element
and their relative abundance.”
CALCULATING
AR
• We take the masses of the isotopes and
multiply them by their relative Abundance
(Mass 1 x Abundance 1)+ (Mass 2 x Abundance
2)= Ar
• Using Chlorine as an example because we
know it has two isotopes; 35 and 37 with
abundances of 75% and 25% respectively…
17 Protons
18
Neutrons
17
Electrons
17 Protons
20
Neutrons
17
Electrons
CHLORINE CAN EXIST IN TWO FORMS
Using the equation you just wrote
in your books, calculate the Ar of
• A) Carbon
masses of
abundance
abundance
has two isotopes with atomic
12 and 13, Carbon 12 has an
of 99% While Carbon 13 has an
of 1% calculate the Ar of Carbon.
• Magnesium has three stable isotopes:
??
Calculate the Ar of Magnesium
A QUICK RECAP:
• When we change the number of protons an element
has, it changes it’s ____________ and becomes a
different ________
• When we change the number of neutrons an element
has, it changes it’s ___________ and it becomes an
_______ of that element
ELECTRON SHELLS
• Rules:
• A) Each shell has a set capacity that once reached, no
more electrons can be placed. That electron starts on
a new shell, further away from the nucleus
• B) Electrons cannot start a new shell unless the previous
Electron shells
Fill up from the centre
•Max 2 in first shell
•Max 8 in second shell
•Max 8 in third shell
•More in next shell
e.g.
Na
11
What are the electron
arrangements for :-
6C
12Mg
20 Ca
ELECTRON
CONFIGURATION
STARTER: ISOTOPE RECEP
• The element rhenium consists of two isotopes 185Re and 187Re,
in the atomic ratio of 2:3. Calculate the relative atomic mass.
• Element X has two isotopes, Element 91X has an atomic
abundance of 60%. The Ar of element X is 94.6. Using this
information find the atomic mass of the other isotope of
element X
ELECTRON
CONFIGURATION
• Now that we know how many particles are present
in an atom, we need to put the electrons into a
regular pattern in their orbits.
• This is known as the electron configuration.
Electron shells
Fill up from the centre
•Max 2 in first shell
•Max 8 in second shell
•Max 8 in third shell
•More in next shell
•Can’t go to the next shell without filling the lower ones
first.
• Sodium has an atomic number of _____. It has
_____ electrons in its atom.
• On the 1st shell, there will be ____ electrons.
• On the 2nd shell, there will be ____ electrons.
• On the 3rd shell, there will be ____ electron.
• The configuration for sodium would be
__,__,__.
• This is a diagram of how
the electron configuration
of sodium would look
like:
• Beryllium (2,2)
• Sulphur (2,8,6)
• Oxygen (2,6)
• Potassium (2,8,8,1)
• Helium (2)
WHAT DO THESE TWO
ELEMENTS HAVE IN COMMON?
RELATIONSHIP BETWEEN THE
ELECTRON CONFIGURATION AND
GROUP NUMBER
• Look at the configuration of the elements in the question
and the group number the element is located.
• Do you notice a relationship?
• The group number of an element tells us the number of
electrons that are on the outer shell of the configuration.
• E.g. Oxygen has ____ electrons on the outer shell, it is found
in group ____.
• However, the elements in Group 0 do not have 0
electrons on the outer shell. Instead, the outer shell is
full, so no more electrons can join that shell.
• Helium (He) has 2 electrons on the outer shell. It is
found in group 0 and not group 2 because only 2
electrons are allowed on the first shell, so it is full!!!!
THE PERIODIC TABLE
Lo: To learn how to use the periodic table to determine
electron configuration
STARTER
• Draw the electron configuration of
Magnesium and label it with it’s
electron configuration.
• Element X has 6 shells, there are
only two electrons on the outer
Identify the real name of Element
X.
LETTING THE PERIODIC TABLE DO
THE WORK
1
2
4
5
6
Period
3
• Group = Columns going along
• Period = Rows going down
• The group an element is in tells us the
number of electrons it has on it’s outer
shell while it’s period tells us how many
shells it has
• For example; Phosphorus would be
Group___ Period ___
QUESTIONS:
• Iodine can be found in group __
Period __ , meaning it has __ shells
and __ electrons on it’s outer shell.
• How many electrons would a group 5
element need to gain in order to have
a full shell?
• How many electrons does Neon have
on it’s outer shell?
H and He
• Helium is the reason we call the
last group 0 instead of group 8. All
group 0 elements besides He
have 8 electrons in their outer
shell.
• Following the logic so far, what
group should we put hydrogen in?
SO WHY DON’T WE?
• Elements that belong to the same
group have similar chemical
properties, even if they have different
physical properties.
• Group 1 metals are all alkali metals,
they are all soft to the point they can
be cut with a knife and they all react
violently with water.
PHYSICAL VS CHEMICAL PROPERTIES
• Group 1 elements are in the same group, so
they have similar chemical properties, but
their physical properties are different.
• Using the table below construct a bar chart
of the melting points of group 1 metals
STARTER
PHYSICAL AND CHEMICAL
PROPERTIES
• Physical Properties: Characteristics of a
substance that can be observed or
measured without changing the chemical
nature of the substance
• Chemical properties: describes the way
that an element or compound reacts
chemically with other substances.
• Can we think of examples of both?
• Thinking back to last lesson, is there any
way we can predict the properties of a
substance?
• The properties of elements show trends as
they descend/ascend groups in the
periodic table
• Using our graphs from last lesson, what
would you estimate the melting point of
Caesium is?
A NEW GRAPH: GROUP 7
Element
•
Atomic
Number
Melting
o
Point (C )
Boiling
o
Point (C )
???
???
Fluorine
Chlorine
Iodine
Astatine
PROPERTIES QUIZ
IONS
18/12/2018
• What is an electrons charge, mass and location
within an atom?
• Write out the numbered electron configuration
for…
a) Sodium
b) Oxygen
• Ion: An atom or molecule with a net charge
due to the loss or gain of at least one
electron. For a full outer shell.
Charge
Mass
Location
+1
1
Nucleus
Neutron
neutral
1
Nucleus
Electron
-1
0
Shells
Proton
IONS
• When an atom needs to lose electrons for a
full outer shell, the ion will be positive.
• When an atom needs to gain electrons for a
full outer shell, the ion will be negative.
• E.g. Potassium needs to _____ _ electron for
a full outer shell. The ion for Potassium is __.
• E.g Nitrogen is in group __, so it needs to
gain __ electrons to have a full shell, so the
ion for Nitrogen is __
•
Work out the ions for the following
elements:
1.
2.
3.
4.
5.
6.
7.
8.
Magnesium (Mg)
Chlorine (Cl)
Aluminium (Al)
Sulfur (S)
Caesium (Cs)
Phosphorus (P)
Hydrogen (H)
Argon (Ar)
HOTSEAT!
• You have 5 minutes to look over
your books at atoms and come up
with at least 1 tricky question that
• Our expert in the hotseat must
time runs out
• If you get a question wrong, our
questioner tells us the right answer
and becomes our expert.
• Whoever is our expert when the
time runs our wins a special
Christmas prize.
```
Arab people

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