atoms, ions, molecules

8/3/2019 Atoms, Ions, Molecules

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Atoms, subatomic particles, symbolsIons

Molecules

Simple chemical formulae

Balancing Equations

E-learning



An element is a pure substance thatcannot be broken down into two or more

simpler substances by chemical means.

Matter is made up of tiny particles.There are 3 kinds of particles.

• Atoms

• Ions• Molecules



Matter is made up of tiny particles.

There are 3 kinds of particles.

• Atoms

• Molecules

• Ions+

+ + +

+ -

- - -

-



Cut a gold foil into half, andhalf, and half …

In the end what would you

be left with… ?

An Atom

Gold Element



Atoms: What is an atom?

An atom is the smallest particle of an element

that can take part in a chemical reaction.

An element contains identical atoms that are

of the same type and size



Atoms: Examples

A piece of aluminium foilconsists of only aluminiumatoms all of which have the

same size

A piece of copper containsatoms that are of a different

size from those in aluminium



Atoms: How small is it?

Diameter of about 0.1 nanometre( 1 x 10−10 metre )

It takes 1 000 000 000 000 000 or 1015

atomsto completely cover the head of a pin

The cross-section of hair can fit 1 000 000 or106 atoms

How small?



Atoms: Subatomic Particles

Atoms are further made up of three types of particles. They are called:

Nucleus

Proton

Neutron

Electrons

Electrons orbit around the nucleus in

a path known as electron shell.



Atoms: Charges of Subatomic Particles

Nucleus

Proton =

positively

charged

Neutron =neutral

Electrons =

negativelycharged

Electrons orbit around the nucleus in

a path known as electron shell.



Atoms: Subatomic Particles

Particle Actual mass

(kg)

Relative

mass

Relative

charge

Found in

Proton

1.67 x 10

-27 1

1+ Nucleus

Neutron 1.67 x 10-27 1 0 Nucleus

Electron 9.11 x 10-31 ≈ 0.0005 1- Shells

(orbitals)



Some Exercises

Particle Relative

mass

Relative

charge

Proton 1 1+

Neutron 1 0

Electron ≈ 0.0005 1-



Structure of an Atom

The nucleus consists of protons and neutrons.

The nucleus has a positive charge, due to the

positively charged protons.

The electrons have negative charges and they

orbit around the nucleus.

Neutrons as the

name suggests, is

neutral



Brilliance of the Periodic Table




Na23

11

Atomic Symbol

of Element

Mass No. or

Nucleon No.

Atomic No. orProton

Number




Hence from the periodic table, you can determine thenumber of protons and neutron. How about the number of

electrons?

In an atom,

the no. of electrons = no. of protons

Atomic (proton) number: is the number of protons in

an atom

Every element has a unique proton number. It does not

change.

Mass (nucleon) number: is the total number of

protons and neutrons in the nucleus.



Some Exercises

Element No. of protons No. of neutrons No. of electrons

8 8 8

6 6 6

4 5 4

56 81 56

18 22 18

16

8O

Ar 40

18

C 12

6

Ba

137

56

Be9

4



More Exercises: Don’t Complain

NucleusElectron

Base on the above diagram, state the number of

protons present in the nucleus?



Summary

Definition of an atom

Size of an atom

Sub-atomic particles and their properties

Symbol for the atom

Atomic number and mass number



What is an atom?

An atom is the smallest particle of an element that cantake part in a chemical reaction.

What are the three subatomic particles that make up

an atom?Protons, Neutrons and electrons

What particles are found in the nucleus of an atom?What electrical charge do they have?

Proton (positively charge)

Neutron (no charge)



What particles move around the nucleus? What electrical

charge do they have?Electrons. Negatively charged.

There is one kind of atom with no neutron. Which atom is it?

The hydrogen atom

What makes one kind of atom different from other kinds of atoms?

Each atom has a unique number of protons

What are the elements in the Periodic Table arranged inorder of?

They are arranged in order of proton number.



Electron Arrangement of Atoms

Nucleus

Proton

Neutron

Electrons

Electronic configuration and electronic structure

refers to the way the electrons are arranged in an atom.




Electrons are arranged in shells around the nucleus

Nucleus

Shell

Electrons

Electrons can be filled in theshell and there is a fixed

number of electrons that cango into each shell.

First shell: maximum of 2electrons.

Second shell: maximum of 8electrons.

Note: The order at which we

draw in the electrons isimportant, North, South, East,West

Third shell: maximum of 8electrons.

Note: The inner shell must be filled in FULLY before moving

on to the outer shell

El A f A




Na

Let’s take a look at an example of drawing an atom, Sodium

From the periodic table, Sodium, Na lookslike this

Therefore Sodium, Na has11 electrons

(1) We start by first

drawing the Symbol

of Sodium.

(2) Draw the 1st shell

(3) The 1st shell can fill

two electrons. Note

the order in which it is

drawn. NSEW

(4) Draw and fill on the 2nd shell with 8 electrons.

(5) Since Na has 11

electrons, we need to

draw a 3rd shell

Key:

represents

electrons of Na





S

Let’s do that again with Sulfur, S atom.

From the periodic table, Sulfur, S looks like this

Therefore Sulfur, S has 16electrons

(1) We start by first

drawing the Symbol

of Sulfur.

(2) Draw the 1st shell

(3) The 1st shell can fill

two electrons. Note

the order in which it is

drawn. NSEW

(4) Draw and fill on the 2nd shell with 8 electrons.

(5) Since S has 16

electrons, we need to

draw a 3rd shell

Key:

represents

electrons of S



Beautiful, NEAT drawings

When drawing an atom, using the CIRCLE stencil (buyfrom book shop) will really help achieve the above.

Key!

All atomic drawing MUST come with a Key! Else wewont know what your means

Electron representation.

We can use a few shapes to represent electrons.

(a) (b) (c)



Electron Configuration of Atoms

F

Electron configuration of atoms is the numerical representationof electrons found in the electron shell .

From the periodic table, fluorine has 9 electrons

Key:

represents electrons of F

Electronic configuration of Fluorine

2.7

This number

represents the numberof electrons in the first

shell

This number

represents the numberof electrons in the

second shell

The addition of these two numbers should give

the total number of electrons of fluorine



Some Exercises (my favorite part cos its not yours.. WAHAHAHA)

Draw the electronic structure and state the electronic

configuration of the first 20 elements.(Yes I say 20 and its not a typo)



Valence electron of Atoms

O

The electrons in the outermost shell is known as thevalence electron.

From the periodic table, Oxygen has 8 electrons

Key:

represents electrons of O

Electronic configuration of Oxygen: 2.6

Number of Valence

electron in Oxygen: 6



The true brilliance of the Periodic Table

Exercise: Your task is to find a pattern between what you have

learnt thus far and the periodic table. As a cool teacher, I’ll give

you a clue. Use the electronic configurations of the first 20

element to find a pattern between it and the periodic table

When you figure it out, you’ll truly feel brilliant



Recall: Charges of Subatomic Particles

Nucleus

Proton =

positively

charged

Neutron =neutral

Electrons =

negatively

charged

The negatively charged electrons are attracted tothe positively charged nucleus by electrostatic force.



Charge of an atom

Base on the charges of the sub-atomic particles,what do you think is the charge on an atom?

An atom has no charge (i.e. electrically neutral)This is because…..

In an atom,

the no. of electrons = no. of protons

The charges on the protons and the

electrons balance each other.



Isotopes

Isotopes are atoms of the same element having the samenumber of protons but different number of neutrons.

Example 1: Hydrogen has 3 isotopes

1

1 H

2

1 H

3

1 H

Protons 1 1 1

Neutrons 0 1 2

Electrons 1 1 1

1

1 H

2

1 H

3

1 H

Hydrogen Deuterium Tritium



Isotopes

Example 2: Carbon has 2 isotopes

Protons 6 6

Neutrons 6 8

Electrons 6 6

Carbon – 12 Carbon – 14

C 12

6

14

6

C

C 12

6

14

6C

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