1. Subatomic Particles

2. REVIEW ATOMS
Atom
An atom is the smallest particle of an element that still has the properties of that element
50 million atoms, lined up end-to-end = 1 cm
An atom = proton(s) + neutron(s) + electron(s)
The Greek root for the word atom, "atomon," means "that which cannot be divided.”

3. The structure of the atom
The Ancient Greeks used to believe that everything was made up of very small particles. Some experiments in 1808 proved this and called these particles ATOMS:
ELECTRON – negative, mass nearly nothing
PROTON – positive, same mass as neutron (“1”)
NEUTRON – neutral, same mass as proton (“1”)

4. The Atom:
Electron
Nucleus
Shell or Orbit

5. The Atom Hydrogen: Proton Electron
Hydrogen has one proton, one electron and NO neutrons

6. The Atom Sodium Valence Shell Electrons Protons Neutrons
Sodium has eleven electrons, eleven protons and twelve neutrons.

7. area surrounding the nucleus
Atomic Theory:
Atoms are made up of smaller particles known as sub-atomic particles.
The nucleus is at the center of an atom.
The nucleus is composed of protons and neutrons.
Electrons exist in the space surrounding the nucleus.
# of protons = # of electrons in every atom
Nuclear charge = charge on the nucleus = # of protons
Atomic number = # of protons = # of electrons
Name
Symbol
Charge
Location
Relative Mass
Proton p 1+
nucleus
1836
Neutron n
Electron e 1–
area surrounding the nucleus 1
See page 170

8. Mass and atomic number 4 He 2 Particle Relative Mass Relative Charge
Proton 1
Neutron
Electron -1
MASS NUMBER = number of protons + number of neutrons He 2 4
SYMBOL
ATOMIC NUMBER = number of protons (obviously)

9. Subatomic Particles
Group 1
Element symbol
1 H
Hydrogen
1.001
Period 1
Element name
Atomic
number
Atomic mass
Atoms are split into subatomic particles (electrons, neutrons, protons)
Nucleons are particles of the nucleus of the atom
These include protons (1 +), neutrons (no charge)
Number of protons in element is the atomic number (ie H has 1 proton)
Electrons have charge (1-) are located outside of nucleus
Neutral atom, their number of electrons equals atomic number (ie. H has 1 electron)

10. SUBATOMIC PARTICLES: (think parts of atoms)
Protons(p): positively charged ions located in the nucleus. Number of protons=atomic number
Neutrons(n): neutral particles located in the nucleus; no charge.
Use the formula
Atomic Mass - Atomic Number= # neutrons

11. Subatomic Particles Continued:
Electrons
exist in space surrounding the nucleus in invisible shells (energy levels)
electrons are transferred or shared between atoms to form chemical bonds
Carry a negative ion charge
Each energy shell has electrons.
First shell always has 2 electrons
Than 8 electrons on each other shell.
MUST REMEMBER:
Atomic Number=# of protons = # of electrons in every atom

12. Charge (if ion)
Atomic Mass
Symbol
Atomic Number

13. EXAMPLE:
How many protons, neutrons and electrons are found in an atom of
133 55 Cs
Mass number = sum of protons and neutrons
Neutrons= Mass # (133) - atomic # (55) = 78
There are 78 neutrons
Atomic Number
How do you get the number of protons?
Protons=Atomic #
How do you get the number of Electrons
Electrons=Atomic #
Therefore, the
Atomic number = protons and electrons
There are 55 protons and 55 electrons in Cesium.

14. H 1 1 Protons: 1 Neutrons: 0 Electrons: 1
Calculate how many protons, neutrons and electrons the element Hydrogen has.
Protons: 1
Neutrons: 0
Electrons: 1 H 1 1

15. Na 23 11 Protons: 11 Neutrons: 12 Electrons: 11
Calculate how many protons, neutrons and electrons the element Sodium has.
Protons: 11
Neutrons: 12
Electrons: 11 Na 23 11

16. Cl 36 17 Protons: 17 Neutrons: 19 Electrons: 17
Calculate how many protons, neutrons and electrons the element Sodium has.
Protons: 17
Neutrons: 19
Electrons: 17 Cl 36 17

17. Al 27 13 Protons: 13 Neutrons: 14 Electrons: 13
Calculate how many protons, neutrons and electrons the element Sodium has.
Protons: 13
Neutrons: 14
Electrons: 13 Al 27 13

18. Re 186 75 Protons: 75 Neutrons: 111 Electrons: 75
Calculate how many protons, neutrons and electrons the element Rhenium has.
Protons: 75
Neutrons: 111
Electrons: 75 Re
186 75

19. REVIEW:
From your knowledge of subatomic particles, fill in the chart below
Element Name
Atomic #
Atomic Mass
# Protons
# Neutrons
# Electrons
Aluminum 12 19 5

20. Focus Questions:
How does the mass of protons compare with the mass of electrons?
What reason could there be for the number of protons being equal to the number of electrons in an electrically neutral atom?
Is a particle an atom if it has no protons?