ch 8 Atomic theory and basic chemistry

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ch 8 Atomic theory and basic chemistry

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The history of the ATOM

Around 500 BC.

( 2500 years ago )

A philosopher named

Democritus was asked:

What is matter made of ?

He thought about it for awhile

and then gave his answer:

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I think Matter is made

of little

“unbreakable things.”For example:

Water is made of little unbreakable

pieces of water

Wood is made of little pieces of wood

Glass is made of little pieces of glass

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But since he was Greek he did not actually say the

word “unbreakable thing” he spoke in Greek so

he said unbreakable in Greek

ATOMHe said matter is made of different types of atoms:

wood atoms

glass atoms

water atoms

steel atoms

air atoms

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But most people did not believe,

Every educated person already knew

that all things were made of a

combination of the 5 basic elements.

Water

Air

Fire

Life

EarthWafles

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What would a super hero made of the 5

elements of matter, look like?

E LFAW

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Captain Planet

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What other

super hero has

Waffle

Powers?

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But later (a few thousand years later) science

was created and people started to look

for answers that could be supported by

observations and proven with

experiments.

Today we know that:

matter is made of Atoms.

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Organized atoms hold information

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What is inside a proton?Using atom smashers scientist are trying to answer this exact question.

Large Hedron Collider was created to help answer this question. It is a 17

mile long underground loop of magnets, pipes and sensors that cost over 10

billion dollars.

The purpose is to smash protons together with enough force and speed to

shatter them into pieces and see what they are made of.13

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FYI Atoms• Atoms are very small, it would take

hundreds of millions of atoms just to make a grain of sand.

• And atoms are made of even smaller subatomic particles.

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Draw this empty chart in you notes.

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Protons

Neutrons

Electrons

Charge Mass Location

+1 (positive)

0 (neutral)

-1 (negative)

1 amu

1/1840

1 amu

nucleus

nucleus

orbit

So how are protons and electrons similar?

They have the same amount of charge.

Draw this empty chart in you notes.

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• The subatomic particles in a helium atom.

How is this model

inaccurate or

misleading?

Relative sizes

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If this were a proton:

Then an neutron would be this size:

And an electron would be this size:

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If this were

the atom,

the nucleus

would be

the size of a

dust speck.

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There are about 100 different atom types.

They are called Elements and each element has a particular number of protons.

Hydrogen atoms have 1 proton

Oxygen atoms have 8 protons

Carbon atoms have 6 protons.

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There are about 100 different atom types.

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How many different things (molecules) can be made with those 100 elements?

billions and billions

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The atomic number of an element is the number of protons (+) in an atom.

protons

neutrons

A carbon nucleus with atomic number 6

C6

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The atomic number of an element is the number of protons (+) in an atom.

protons

neutrons

A carbon nucleus with atomic number 6

A helium nucleus with atomic number 2

C6

12

He2

5

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protons

neutrons

A carbon nucleus with a mass of 12

protons

neutrons

A helium nucleus with mass of 5

The Mass of an element is the number of protons and neutrons in an atom.

C6

12

He2

5

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Atoms of the same element that differ in the number of neutrons are known as

isotopes

All atoms of Helium have 2 protons

But not all Helium atoms have 2 neutrons

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Some have 3Some have 1 Some have 2

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isotopes• same name,

• same atomic number

• different mass (due to the neutrons)

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On the periodic table the mass of Mercury

(Hg) is 200.6

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How many atoms are

there in the universe that

have a mass of 200.6?

None!

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On the periodic table the mass of Mercury

(Hg) is 200.6

Most Mercury atoms have:

80 protons and 121 neutrons (80+121=201)

Some Mercury atoms have:

80 protons and 120 neutrons (80+120=200)

The mass on the table is listed as 200.6,

this is the average mass.There are no atoms in the universe with a mass of 200.6

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The number of electrons (-) in an atom is normally the same as the number of protons (+).

( The amount of + and – must be balanced )

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protons

neutrons

A carbon nucleus with a mass of 12

protons

neutrons

A helium nucleus with mass of 5

C6

12

He2

5

Carbon will have 6

electrons

Helium will have 2

electrons

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Since isotopes always have the

same number of protons (+),

they always have the same

number of electrons (-).

Isotopes act exactly the same.

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Some isotopes of very stable atoms

are unstable.

That means they are radioactive

and may decay. (fall apart and turn into some other element)

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Radioactive isotopes can be used:• to determine the ages of rocks and fossils.

• to treat cancer patients. (killing cancer cells)

• to kill bacteria (and preserve food).

• as labels or “tracers” to follow the movement of substances within an organism.

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It is the number of electrons that

determines how an atom will act.

A behavior of an atom is called a

chemical property

For example some atoms (like Sodium),

explode when they are mixed with water

(because of its electrons).

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Chemical CompoundsYou are 65% Oxygen, and you are 80% water.

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Chemical CompoundsYou are 65% Oxygen, and you are 80% water.

but most of the oxygen atoms are combined with Hydrogen atoms to form water molecules.

Water is a compound because it is a molecule with two different elements combined together

In nature, most elements are found in molecules combined to other elements.

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The physical and chemical properties of a compound are different from the elements from which it is formed.

IOW: the stuff you make can be completely different from what you started with.

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Sodiumhighly reactive metal that explodes in water

41Click on video

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Chlorinepoisonous gas

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Click on video

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Sodiumhighly reactive metal that

explodes in water

Chlorinepoisonous gas

sodium chloride

salt

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chemical formulas

The formula for Water is - H2OThis tells us that a molecule contains

two atoms of hydrogen one atom of oxygen.

The formula for salt is - NaClThis tells us that a molecule contains

one atoms of Sodium and one atom of Chlorine.

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Chemical Bonds connect atoms together.

Bonds result from the interaction of electrons.

Only the electrons in the outer layer interact.

Outer layer electrons are called valence electrons

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A jaw breaker’s

flavor depends

only on the

outermost layer.

The valence layer

Pizza flavor

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chemical properties are determined by the number of valence electrons.

(not on the total number of electrons)

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How hard it is to break into a building depends on the number of

guards outside.

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ions: atoms that do not have a balanced number of

electrons and protons

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How do you make a negative ion?

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By adding electrons to the atom.

When an atom gains electrons it becomes a negative ion (-)

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How do you make a positive ion?

This is one of the most often missed test questions.

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By taking electrons from the atom.

When an atom loses electrons it becomes a positive ion (+)

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Protons +17

Electrons - 18

Charge -1

Protons +11

Electrons - 11

Charge 0

Protons +11

Electrons - 10

Charge +1

Protons +17

Electrons - 17

Charge 0

Chlorine ion (Cl-)Sodium atom (Na)

Chlorine atom (Cl)Sodium ion (Na+)

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Resources/Movies/vaenergy.mov

Resources/Movies/vaenergy.mov

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ionic Bond: formed when positive and negative ions stick together. (opposites attract)

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Protons +17

Electrons - 18

Charge -1

Protons +11

Electrons - 11

Charge 0

Protons +11

Electrons - 10

Charge +1

Protons +17

Electrons - 17

Charge 0



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Covalent Bond: formedwhen valence electrons are shared by atoms

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As long as they are

sharing the potato

sack they are stuck

(bonded) together.

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The hydrogen atoms are bonded to the oxygen atoms because they share electrons.

Covalent Bond

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The uneven distribution of electrons causes polarization, and makes the molecule have positive and negative ends.

Water molecules

are very polarized.Negative

end

Positive

end

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What do group ( 1 ) elements all have in common.

They all have 1 electron in the outer most shell (valence electrons)

Since chemical properties (behavior) depends on the number

of V.E. these elements will all “act” the same.

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They all have 7 electrons in the outer most shell (valence electrons) all “act” the same.

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They all have full outer most shell ( 0 valence electrons) and all

“act” the same. Actually they don’t act at all, they just sit there

not interacting with other elements. (Nobel gasses)

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Atoms want to have a full outer shell, just like

the Nobel Gasses.

Who wants to be like the nobles?

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Some atoms try to gain electrons to fill their

shells to be like NG. (greedy takers)

We call these “non-metals”.

Some atoms try to give away electrons so their

outer shells are full like NG. (generous givers)

We call these the “metals”.

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Dark blue are givers / Light blue are takers

non-metals (greedy)metals (generous)

This chart divides the takers from the givers.

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What about the purple?

These can’t decide what they want to do, sometimes they take, sometimes they give.

semi-metals or metalloids

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Electronegativity:a measure of how much

attraction the atoms

have for extra electrons.

The type of bond

between atoms depends

on how greedy /

generous the atoms are.

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Giver with a Taker

electrons are stolen

Metal with a Non-metal

electrons are stolen

This creates a positive ion and a negative ion

ionic bond between them.

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Protons +17

Electrons - 18

Charge -1

Protons +11

Electrons - 11

Charge 0

Protons +11

Electrons - 10

Charge +1

Protons +17

Electrons - 17

Charge 0



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Taker with a taker

Non-metal with a Non-metal

electrons are shared

As long as two atoms are trying to hold on

to the same electron, they are bonded.

covalent bond

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The hydrogen atoms are bonded to the oxygen atoms because they share electrons.

Covalent Bond

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Giver with a giver

metal with a metal

electrons are shared constantly

being given and re-given

Basically the electrons are continually moving

between atoms

metallic bond (allows of metals)

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Atom role playing with class, show bonds

between greedy and generous.

metals

non-metals

metalloids

noble gasses

The Quiz is next

1 – 10Questions may have

more than one

correct answer.

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The particles that are outside the nucleus of an atom are called

A. neutrons.

B. protons.

C. electrons.

D. isotopes.

E. None of the above

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The atomic number of carbon is 6. How many neutrons does the carbon-14 isotope have?

A. 6

B. 8

C. 12

D. 14


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Which of the following statements about the isotopes of carbon is true?

A. They are all radioactive.

B. They have different numbers of electrons.

C. They have the same chemical properties

D. They have different atomic masses.

E. They have the same number of protons

F. None of the above

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A Chemical compound consists of:

A. Electrons mixed with neutrons.

B. two or more elements combined in a definite proportion.

C. Many un-bonded elements.

D. Pure substances like water and alcohol


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What type of bond would occur between:Chromium and Tungsten

A. ionic

B. metallic

C. covalent

D. no bonding will occur

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What type of bond would occur between:Oxygen and Calcium

A. ionic

B. metallic

C. covalent


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What type of bond would occur between:Fluorine and Iodine

A. ionic

B. metallic

C. covalent


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What type of bond would occur between:Argon and Iron

A. ionic

B. metallic

C. covalent


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If an ionic bond forms betweenArsenic and Mercury , which ion

would have the positive charge?

A. Mercury

B. Arsenic

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If a covalent bond forms betweenArsenic and Bromine, which side of

the polarized molecule would be negative?

A. Bromine

B. Arsenic

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ch 8 Atomic theory and basic chemistry

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Transcript of ch 8 Atomic theory and basic chemistry