The Nucleus

The Atom's Structure: Nucleus vs. Electron Cloud

The Atom's Structure (Quick Review)

• The atom consists of a nucleus and an electron cloud.

  • The nucleus contains protons and neutrons.

  • The electron cloud holds electrons.

MASS OF THE ATOM  = NUCLEUS  

Just about all of the mass of an atom comes from the protons & neutrons found in the nucleus.

Think of electrons as dust on your shoulder.

VOLUME (SPACE IT TAKES UP ) OF THE ATOM  = ELECTRON CLOUD

Nucleus: is extremely tiny. It hardly takes up any space.

Analogy:  Nucleus = a marble on the 50 yard line in a stadium

 

Electron Cloud:  The rest of the atom consists of space for the electrons to zip around in. 

Analogy:    Electrons = people in the stands. 

   Electron Cloud = All of the seats in
the stadium.  Very few are
occupied.  Most are empty.

   Energy Levels = Specific rows within
the stadium (electron cloud). 

 

MOST OF AN ATOM IS EMPTY SPACE!

Since electrons are so unbelievably tiny, most of the electron cloud is just empty space!

  Analogy: 20 people in Giants Stadium. 
Most of the seats are empty. 

 

Multiple Choice

Where is most of the mass of an atom concentrated?

• Nucleus

• Electron Cloud

• Both Nucleus and Electron Cloud

Multiple Choice

What determines the volume of an atom?

• Nucleus

• Electron Cloud

• Both Nucleus and Electron Cloud

Multiple Choice

What is the main difference between the nucleus and the electron cloud in an atom?

• The nucleus contains protons and neutrons, while the electron cloud holds electrons.

• The nucleus is much larger than the electron cloud, occupying most of the atom's volume.

• The electron cloud contains protons and neutrons, while the nucleus holds electrons.

• The electron cloud is much smaller than the nucleus, occupying most of the atom's volume.

PROTONS PULL ELECTRONS CLOSE:

Protons: + Electrons: -    
They have opposite charges so they are attracted to one another.

The more protons in the nucleus, the stronger the attraction between the nucleus and the electrons in the electron cloud. 

 

STRONGER NUCLEUS = SMALLER ATOM:

More protons exert a stronger attraction for the electrons in the electron cloud.  They get pulled in closer to the middle and atom gets smaller.

 

Multiple Choice

Which atom from row 4 on the periodic table will be smaller?

• K

• Ca

• As

• Br

Multiple Choice

Protons exert an ___ force on electrons in the electron cloud.

• attractive

• neutral

• positive

• repulsive

Complete your Take Away Ideas before you submit this lesson and move on to Part 8.