John dalton william crookes j j thomson ernest rutherford
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John Dalton William Crookes J.J. Thomson Ernest Rutherford. Early Theories About ATOMS. 4 Materials:. ATOMS. (2500 years ago). -Earth -Fire -Air -Water. Ancient Greeks-. -Ex. Wood= Earth+Fire. Early Theories About ATOMS. “Cannot be divided” solid spheres-

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John Dalton William Crookes J.J. Thomson Ernest Rutherford

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John dalton william crookes j j thomson ernest rutherford

John DaltonWilliam CrookesJ.J. ThomsonErnest Rutherford


Atoms

Early Theories About ATOMS

4 Materials:

ATOMS

(2500 years ago)

-Earth -Fire

-Air -Water

Ancient Greeks-

-Ex. Wood= Earth+Fire


Early theories about atoms

Early Theories About ATOMS

“Cannot be divided” solid spheres-

(No one believed him) (930 BC)

Democritus(Greek thinker) – All matter is made up of Atoms


1808 john dalton

1808 John Dalton

Proved that matter is made up of Atoms

Different elements

have different masses


1808 john dalton1

(By putting substances together to form new substances and taking them apart chemists discovered that ALL matter is made of elements)

1808 - John Dalton

Element – matter made of atoms of only one kind (periodic table of elements)


1870 william crookes

1870 - William Crookes

Used a cathode ray tube to show streams of particles


1897 j j thomson

(opposite side)

1897 - J.J. Thomson

Plum Pudding

model

Discovered the Electron

Bent Crookes stream with a magnet

did this with many gases and many elements

http://www.aip.org/history/electron/jjsound.htm


1911 ernest rutherford

Used by modern scientists

1911 - Ernest Rutherford

The Nuclear Atomic Model


1911 ernest rutherford1

1911 - Ernest Rutherford

  • protons & neutrons

  • positive charge

The Nucleus – the small central core of an atom where most of the mass is located

  • (electrons found in a cloud around it)


Electron cloud

Electron Cloud -

Region around the nucleus in which the electrons travel

DaltonThomson Rutherford


John dalton william crookes j j thomson ernest rutherford

DaltonThomson Rutherford


Atomic particles

Particle charge found

Electron- negative outside nucleus

Atomic Particles-

Proton + positive inside nucleus

Neutron No charge inside nucleus

The basic building blocks of atoms

Proton

Protons = electrons

neutral atom

Neutron

Electron


Size of atomic particles

VERY SMALL!!

Atomic Mass Unit (u) – A unit used to express the masses of atomic particles and atoms (1u=1.66 x 10-27Kg)

Size of Atomic Particles-

Sooooo small that scientists use:

Electron0 u (1/1836)

Proton 1 u

Neutron 1 u (1837/1836)


Scientific models

Ex. Stars, Atoms

Scientific Models -

-Used when objects can’t be studied directly

  • Many experiments

  • (how do atoms behave under different conditions)


Atomic number the number of protons in the nucleus of an atom

Element #of protons # of electrons

Hydrogen1

Oxygen8

Sulfur16

Gold79

1

8

16

79

Atomic Number - The number of protons in the nucleus of an atom

In a normal atom positive charges (proton) cancel out negative charges (electrons)


Electrons in motion

Electrons in motion

1913 –Niels Bohr – electrons can follow only certain orbits


Electron arrangement

Electron Arrangement

Ex. He

+

Energy Level – A region around an atomic nucleus in which electrons move

Ex. C

Nucleus

2 8 18 32

+


Symbols of elements berzelius swedish scientist

Symbols of Elements - Berzelius (Swedish Scientist)

1st letter – ALWAYS CAPITALIZED

2nd letter(if there is one) – ALWAYS lower case

Atomic Symbol – 1 or 2 letters used to represent an atom of an element

- Based on the element name

(sometimes the Latin name)


The periodic table of elements

The Periodic Table of Elements


Symbols of elements

Name of Element

Atomic Number

Symbol

Atomic Mass

Symbols of Elements

Hydrogen

1

H

1.008


The number of particles in a nucleus

Protons = Electrons

Mass Number = Protons + Neutrons

Mass Number – The sum of the protons and Neutrons in an atom

The Number of Particles in a Nucleus

(different atoms have different mass #’s)


John dalton william crookes j j thomson ernest rutherford

4

3

5

11

5

14

7

7

3

10

10

10


Isotopes atoms whose nuclei contain the same of protons but different s of neutrons

Isotopes- Atoms whose nuclei contain the same # of protons, but different #s of Neutrons

Ex. Hydrogen-1, Hydrogen-2, Hydrogen-3

(deuterium) (tritium)

+

+

+


Atomic mass the average of all the masses of the isotopes of a particular element

Atomic Mass- The average of all the masses of the isotopes of a particular element

-Round to the nearest whole #= Mass #


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