Instructional Objective:1.Learn the atomic models

2.Learn the atomic structure and elements.

History of the Atomic Model

The Greek Model

Dalton’s Model

Thomson’s Model

Rutherfords Model

Bohr’s ModelThe Wave-

Particle Model

The Greek Model

• Proposed around 400 B.C. By the Greek Philosopher Democrats

• Called them “Atomos”, in Greek means can’t be divided or destroyed.

John Dalton’s Model

Proposed the Atomic Theory in 1803

All atoms are made up of solid indivisible particles.

* Elements differ in their atom’s size

J. J. Thomson’s Model

• Believed that protons and electrons were mixed together

• Known as the “plum pudding” or

Proposed in 1897

“raisin bread”model

Ernest Rutherford’s Model

• Proposed in 1907 after discovering atom’s nucleus

• Electrons move around a central nucleus

.containing protons.

Niels Bohr’s Model

• Electrons move in energy levels around a central nucleus

• Electrons can only be in these energy levels.

Particle-Wave Model

• James Chadwick discovers neutron in 1935.

• Electrons are most likely found in energy levels

What is an Atom?*The smallest unit of a matter is known as

an atom

What is an element?• An element is made up of only one kind

of atom.What is a molecules ?• Is the smallest unit of a compound What is a substance?• any element or compound

Structure of an atom

• An atom is made up of a nucleus that contain protons and neutrons.

• And an outer orbit that contain electrons.

-Protons are always positive in charge-Electrons are negative in charge -Neutrons are neutral or without any

charge

Characteristics of an Atom

• Atom itself has no charge because protons are always equal to electrons.

• Ex: Sodium –Protons are 11 --Electrons are also 11 ( Positive and negative will cancel each

other)

Properties of subatomic particles• Protons, electrons and neutrons are the

subatomic particles• Protons are always positive in charge• Electrons are negative in charge• Neutrons are neutral or with out any charge

Difference between atomic mass and Atomic number

• Atomic mass: is the total number of protons and neutrons in the nucleus.

• Atomic number: Is the total number of protons

Element Block from periodic table

• 17 ---- atomic number Cl ---- Symbol

Chlorine –Name 35.45 --- atomic mass or mass number

1717

ClCl ChlorineChlorine

35.4535.45

Other Symbols to remember

p+ →Proton(always positive charge)e- → electron (always negative in charge)N0 → Neutrons(zero charge)<→Less than> →greater than+ → and or plus→ → yield (s) → solid(l) → Liquid(g) → gas

ISOTOPES.

• Atoms of the same element that have different number of Neutrons.

• Ex: The most common isotope of hydrogen. -Hydrogen has no neutrons at all(1proton) -Deuterium, with one neutron.

(1proton+1neutron)

- Tritium, with two neutrons.(1proton+2 neutrons)

          

       

                 

 

       

               

 

Isotopes can be written asthe part of a chemical symbol

• Ex: 15 7N or Nitrogen – 15 ( 15 is the mass number and 7 is the atomic number)

• Ex: 3517Cl or Chlorine -35( 35 is the mass

number and 17 is the atomic number)• Close to the atomic mass, abundant is

the element in that Isotope.

How are electrons arranged in an atom

Electron Cloud• The area in an atom where electrons are

foundEnergy levels• Is the place in the electron cloud• Are in different distance from nucleus• The closest to nucleus –less and weak• Far away from nucleus –more and more

powerful

The energy levels• 1st- contain maximum 2• 2nd- contain maximum 8• 3rd- contain maximum 18• 4th - contain maximum 32

Electron Configurations* Is the arrangement of electrons in the orbitals of an atom.

Electron configuration

•S orbit- 2 electrons•P orbit-6 electrons•D orbit-10 electrons•F orbit – 14 electrons