Atoms 0 Matter is anything that takes up space and has mass. http:// - - PowerPoint PPT Presentation

The Element Song

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Atoms

0Matter is anything that takes up space and has mass.

All matter is made of atoms.

0Atoms are the basic building blocks of matter. They

make up everything around us; Your desk, the board, your body, everything is made of atoms!

0Atoms are too small to see without powerful

microscopes.

Atomic Structure

There are two basic components in every atom: Electron Cloud Nucleus

Subatomic Particles

Three subatomic particles make up every atom:

Subatomic Particle Charge Location Proton Positive (+) Nucleus or “Core” Neutron No Charge (0) Nucleus or “Core” Electron Negative (-) Electron Cloud

Subatomic Particles

Electron Cloud:

• Electrons orbit the

nucleus. Nucleus or “Core”:

• Protons and Neutrons

are found in the nucleus.

Atomic Theory

Changes over time…

Atomic Theory

0Because we cannot see atoms, we use models to teach

and learn about atoms.

0The atomic theory has changed over time as new

technologies have become available.

0 Remember: Scientific knowledge builds on past research and experimentation.

Democritus

■ 460 BC - Greek philosopher proposes

the existence of the atom

■ He pounded materials until he made

them into smaller and smaller parts

■ He called them atoma which is Greek for

“indivisible”.

Democritus

■His Theory:

All atoms:

■ Are small hard particles ■ Are made of a single material formed into

different shapes and sizes

■ Are always moving, and they form different

materials by joining together

Atomic Theory Timeline

Scientist Information Model

John Dalton All matter is made of atoms. Atoms are too small to see, indivisible and

• indestructible. All atoms of a

given element are identical.

John Dalton

■ 1803 - British chemist; elements combine

in specific proportions to form compounds

Solid Sphere Model or Bowling Ball Model Proposed by John Dalton

John Dalton

■ His Theory:

▪ All substances are made of atoms that cannot

be created, divided, or destroyed.

▪ Atoms join with other atoms to make new

substances.

▪ Atoms of the same element are exactly alike,

and atoms of different elements are different in mass and size.

Dimitri Mendeleev (Men-da-lay-ev)

■ In 1869 Russian chemist Dimitri Mendeleev

started the development of the periodic table, arranging chemical elements by atomic mass. He predicted the discovery of

• ther elements, and left spaces open in his

periodic table for them.

Scientist Information Model

J.J. Thompson

Discovered the negative electron, and predicted that there also must be a positive particle to hold the electrons in place.

Atomic Theory Timeline

J.J. Thomson

■ 1897 - English chemist and physicist;

discovered 1st subatomic particles

Plum Pudding Model or Raisin Bun Model Proposed by J.J. Thomson

J.J. Thomson

■His Theory:

■ Atoms contain negatively charged particles

called electrons and positively charged matter.

■ Created a model to describe the atom as a

sphere filled with positive matter with negative particles mixed in

■ Referred to it as the plum pudding model

Scientist Information Model

Ernest Rutherford Discovered the nucleus of an atom and named the positive particles in the nucleus “protons”. Concluded that electrons are scattered in empty space around the nucleus.

Atomic Theory Timeline

Ernest Rutherford

■ 1912 - New Zealand physicist discovered

the nucleus

Nuclear Model Proposed by Ernest Rutherford

Ernest Rutherford

■His Theory:

▪ Small, dense, positively charged particle

present in nucleus called a proton

▪ Electrons travel around the nucleus, but their

exact places cannot be described.

▪ Conducted the Gold Foil Experiment

Atomic Theory Timeline

Scientist Information Model

Neils Bohr Concluded that electrons are located in planet-like orbits around the nucleus in certain energy levels.

Niels Bohr

■ 1913 - Danish physicist; discovered

energy levels

Bohr Model or Planetary Model Proposed by Niels Bohr

Niels Bohr

■His Theory:

▪ Electrons travel around the nucleus in definite

paths and fixed distances.

▪ Electrons can jump from one level to a path in

another level.

Erwin Shrodinger

■ 1924 - Austrian physicist; developed the

electron cloud model

Electron Cloud Model Proposed by Erwin Schrodinger

Erwin Shrodinger

■His Theory:

▪ The exact path of electrons cannot be

predicted.

▪ The region referred to as the electron cloud,

is an area where electrons can likely be found.

Scientist Information Model

James Chadwick Discovered that neutrons were also located in the nucleus of an atoms and that they contain no charge.

Atomic Theory Timeline

James Chadwick

■ 1932 - English physicist; discovered

neutrons

■ His Theory:

▪ Neutrons have no electrical charge. ▪ Neutrons have a mass nearly equal to the

mass of a proton.

▪ Unit of measurement for subatomic particles

is the atomic mass unit (amu).

Scientist Information Model

(Many Scientists!)

The Modern Atomic Theory

Electrons do not orbit the nucleus in neat planet-like

• rbits but move at high

speeds in an electron cloud around the nucleus.

Modern Theory of the Atom

■ Atoms are composed of three main subatomic

particles: the electron, proton, and neutron.

■ Most of the mass of the atom is concentrated in

the nucleus of the atom.

Modern Theory of the Atom

■ The protons and neutrons are located within

the nucleus, while the electrons exist outside of the nucleus.

■ In stable atoms, the number of protons is equal

to the number of electrons.

Modern Theory of the Atom

■ The type of atom is determined by the number

• f protons it has.

■ The number of protons in an atom is equal to

the atomic number.

Modern Theory of the Atom

■ The sum of the number of protons and

neutrons in a particular atom is called the atomic mass.

■ Valence electrons are the outermost electrons.

Atom

electron Proton Neutron

Atom

Electrons Protons Neutrons

Nucleus Electron clouds

Atomic Number =

number of protons

Atomic Weight =

number of protons + number of neutrons

Protons =

Number of electrons

K

39.0938

19

Atomic Weight = number of protons + number of neutrons

39.0938 = 19 + neutrons

• 19 -19

20.0938 neutrons

There cannot be 0.0928 of a neutron, so this number is rounded to 20 neutrons.

Potassium

H Alkali Metals Hydrogen Alkaline Earth Metals Transition Metals Halogens Noble Gases Inner Transition Metals

H Alkali Metals Hydrogen Alkaline Earth Metals Transition Metals Halogens Noble Gases Inner Transition Metals Li Na K Rb Cs Fr Be Mg Ca Sr Ba Ra F Cl Br I At He Ne Ar Kr Xe Rn

H Alkali Metals Hydrogen Alkaline Earth Metals Transition Metals Halogens Noble Gases Inner Transition Metals Li Na K Rb Cs Fr Be Mg Ca Sr Ba Ra F Cl Br I At He Ne Ar Kr Xe Rn

METALS

NONMETALS metalloids

H Alkali Metals Hydrogen Alkaline Earth Metals Transition Metals Halogens Noble Gases Inner Transition Metals Li Na K Rb Cs Fr Be Mg Ca Sr Ba Ra F Cl Br I At He Ne Ar Kr Xe Rn B Si Ge As Sb Te Metalloids = Semimetals

Metals

• Metals are lustrous

(shiny), malleable, ductile, and are good conductors of heat and electricity.

• They are mostly solids

at room temp.

• What is one exception?

Nonmetals

• Nonmetals are the
• pposite.
• They are dull, brittle,

nonconductors (insulators).

• Some are solid, but

many are gases, and Bromine is a liquid.

Metalloids

• Metalloids, aka semi-metals

are just that.

• They have characteristics of

both metals and nonmetals.

• They are shiny but brittle.
• And they are semiconductors.
• What is our most important

semiconductor?

Adapted by J. Phillips

• Each row is called a “period”
• The elements in each period have

the same number of shells

www.chem4kids.com

• Each column is called

a “group”

• Each element in a

group has the same number of electrons in their outer orbital, also known as “shells”. Except for He, it has 2 electrons

• The electrons in the
• uter shell are called

“valence electrons” www.chem4kids.com

• Transition Metals

have slightly different rules for shells and valence electrons.

• This is something

you will learn about in High School Chemistry. www.chem4kids.com

www.chem4kids.com www.chem4kids.com

• Helium is the exception in Group 8.
• Since it has just one shell, that shell can
• nly fit 2 electrons instead of 8.
• It is in this group because all the elements

have a full outer shell.

Have a great day!