atomic structure and isotopes

7/29/2019 Atomic Structure and Isotopes

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Chapter 4

Atoms and their structure


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Modern View

The atom is mostlyempty space.

Has two regions.

Nucleus-Electron cloud-


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Structure of the Atom

There are two regions.1. The nucleus- contains protons and

neutrons. Positive charge.

Almost all the mass.

2. Electron cloud- most of the volumeof an atom (empty space).

The region where the electron can be found.


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Subatomic particles

Electron

Proton

Neutron

Name Symbol Charge

Relativemass

Actualmass (g)

e-

p+

n0

-1

+1

0

1/1840

1

1

9.11 x 10-28

1.67 x 10-24

1.67 x 10-24


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Counting the Particles

Atomic Number

Atomic Mass

Atomic Number= number of protons (# p)

# of protons determines kind of atom.

Helps find the atom in the periodic table

In neutral atom, atomic number = # of e Atomic mass - avg mass of all isotopes of the atom

Mass Number = (rounded atomic mass) # p + # n

All the things with mass.

NOT on the periodic table


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Example

if an element has an atomicnumber of 34 and a mass number

of 79 what is the

number of protons

number of neutrons

number of electrons

Name


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Element Symbol AtomicNumber AtomicMass MassNumber Number ofProtons NumberofElectrons

NumberofNeutron

s

23Na

K 39 19

38 38 50F 10

20 40 18

50 50 69127I

24Mg

Atomic Structure Video
http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa_pre_2011/atomic/atomstrucact.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa_pre_2011/atomic/atomstrucact.shtml


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Isotopes

Dalton was wrong.Atoms of the same element not

identical, may have different masses.

called isotopes

different number ofneutrons .

Do isotopes of an element have the

same number of protons? Electrons?


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Nuclear Symbols

Contain the symbol of the element, themass number and the atomic number.

XMassnumber

Atomic

number


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Naming Isotopes

Can also be represented as follows: Put the mass number after the name

of the element.

carbon- 12 carbon -14

uranium-235


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Symbols

Find thenumber of protons

number of neutrons

number of electrons

Atomic number

Mass Number

Name

Na2411


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Symbols

Find thenumber of protons

number of neutrons

number of electrons

Atomic number

Mass Number

Name

Br8035


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Symbols

if an element has 91 protons and140 neutrons what is the

Atomic number

Mass number

number of electrons

Complete symbol

Name


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Symbols

if an element has 78 electrons and117 neutrons what is the

Atomic number

Mass number

number of protons

Complete symbol

Name


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Atomic Mass

Is not a whole number because it is anaverage.

are the decimal numbers on the periodic

table.

atomic structure and isotopes

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