Atomic Model

Matter Anything that has mass and volume

– Mass the amount of particles making up a substance

– Volume is the amount of space taken up by the particles

The basic unit of matter is the atom, which is made up of protons, neutrons and electrons

Proton Positively charged (+) Located in the nucleus Mass number of 1 Atomic Number = Number of Protons

– Atomic number on the periodic table– Gives the identity of the atom

Neutron No charge (neutral) Located in the nucleus Mass number of 1 Mass of atom = protons + neutrons

– Must have a whole number of neutrons– Average mass can be found on the

periodic table Neutron number may be different to

form an isotope

Electron Negatively charged (-) Constantly, randomly moving around

the nucleus in energy levels Mass number of 0 If the atom is neutral (has a charge of

zero) then:– Proton number = electron number

Electron number may change to form an ion– An atom with a + or - charge

Determining amount:

How many protons, neutron and electrons are in an atom of Lead:

82

PbLead

207.2

Atomic Number

Element Symbol

Element Name

Atomic Mass

Determining amount How many protons, neutron and electrons are

in an atom of Lead: Number of protons = atomic number

– Atomic number = 82 = # of protons Number of electrons = number of protons

– 82 = # of electrons

Atomic mass = protons + neutrons207.2 = 82 + x

x = 125.2 must be a whole number

125 = number of neutrons

Try one on your own

How many protons, neutrons and electrons are in an atom of silver:

47

AgSilver

107.9

Atomic Number

Element Symbol

Element Name

Atomic Mass

Model of atom

Nucleus

2nd energy level _____ (can hold 8 electrons)

4th energy level _____ (can hold 8 electrons)

3rd energy level _____ (can hold 8 electrons)

1st energy level _____ (can hold only 2 electrons)

An atom can only be represented by a model since the electrons are in constant random motion.

Model: Atom of Sulfur (S)

Nucleus

2nd 8e-

4th ____

3rd 6e-

1st 2e-

Atomic number = 16Determine total number of electrons

Electrons

The number of electrons in the highest energy level determines the behavior and characteristics of the element

Electrons in the highest energy level are valence electrons