1. Atoms and Subatomic Particles Ch 4. Section 2

2. How big is an atom? An atom is incredibly small
The diameter of an atom would have to be increased 200 million times to have the diameter of a penny
If an apple were enlarged to the size of the Earth, the atoms in the apple would be the size of cherries

3. What is an atom made of? Subatomic particles:
Neutron, proton, electrons
A central, dense nucleus (neutrons & protons) surrounded by electrons
Electrons have a negative charge (-)
Protons have a positive charge (+)
Atom is held together by the attraction of electrons and protons
Neutrons are neutral

4. How much does an atom weigh? (What is it’s mass?)
Atoms are so small that it is impractical to use grams
1 atom ͌ g
Instead atoms are measured in atomic mass units or amu’s
One carbon atom is 12.0 amu’s and all atoms are compared to this

5. Atoms - Molecules - Ions
Subatomic Particles
Particle Mass (kg) Mass (amu) Charge
Electron x
Proton x
Neutron x
Most of the mass in an atom is in the nucleus

6. ATOMIC FACTS
Most of the mass of an atom is in the nucleus: the protons and neutrons
The size of the neutron relative to the size of the atoms is like a penny in the middle of a baseball field
The number of protons and electrons need to be equal so that the atom has no charge

7. ATOMIC NUMBER The number of protons in the nucleus of an atom
Atomic numbers of naturally occurring elements:
Lowest=Hydrogen (H)
Z=1
Highest=Uranium (U)
Z=92
Periodic Table of Elements

8. ATOMIC NUMBER Remember,
The number of protons in the nucleus of an atom equal the number electrons so,
Atomic number=
Number of protons=
Number of electrons

9. Mass Number
Sum of the number of protons and the number of neutrons in the nucleus of the atom:
Mass number=# of protons + # of neutrons
And…..
Mass number=atomic number + # of neutrons
# of neutrons=mass number – atomic number

10. Isotopes
Atoms of an element that have the same number of protons and electrons but different numbers of neutrons.
Hydrogen isotopes
Hydrogen has 1 proton, 1 electron and 0 neutrons
Deuterium has 1 proton, 1 electron and 1 neutron
Therefore, it is heavier than hydrogen but has similar chemical properties and slightly different physical properties
Tritium has 1 proton, 1 electron and 2 neutrons

11. Atomic Masses Atomic mass ͌ Mass number Here’s why
They are close but not the same
Here’s why
Mass number is an exact number & atomic mass is a weight so it’s an inexact number
Hydrogen has a mass number of 1 (1 protron + 0 neutrons),
But weighs: amu
Atomic masses are calculated based on the percentage of isotopes present in natural world
H=99.985%; D=.015%; T=trace
Atomic mass of H is:
Periodic table of elements

12. Chemical Basis of Life Most common elements in living organisms
Carbon (C): 9.5%
Hydrogen (H): 63%
Oxygen (O): 25.5%
Nitrogen (N): 1.4%

13. Macrominerals Minerals we need a lot of Calcium (Ca) Phosphorous (P)
Magnesium (Mg)
Potassium (K)
Sodium (Na)

14. Microminerals Needed in small quantities Iron (Fe) Copper (Cu)
Chromium (Cr)
Fluoride (F)
Iodine (I)
Selenium (Se)
Molybdenum (Mo)
Zinc (Zn)