Atoms: building blocks of all matter.

1

• Atoms building blocks of all matter.
• 1012 (one trillion) atoms would fit on the period
  at the end of a sentence.
• The atom is mostly space-the distance from the
  nucleus to the electrons is about 100,000 times
  the radius of the nucleus
• .

2

• Example
• If the nucleus of an atom was the size of a
  baseball, the nearest electron would be high up
  in the stadium bleachers.

3

• Atomic Number the number of protons in a
  particular nucleus.
• Each element has its own unique atomic number.
• Ex. Oxygen is 8, so it has 8 protons.
• In a neutral atom, this is also how many
  electrons are in the atom.
• Ex. Oxygen has 8 electrons

4

• Atomic Mass mass of the protons plus the
  neutrons in an atom
• Proton and Neutrons are each about 1 amu
  (atomic mass unit.)
• 1 amu 1.67 x 10-24 grams

5

• Electrons (e-) are 1/2000 the mass of protons and
  neutrons!
• Theyre so small they are not considered to
  contribute any mass to the atom.

6

• Energy Levels Electrons are arranged in energy
  levels around the nucleus. Each level can hold a
  certain number of electrons (like a book shelf)
• The outermost level is called the valence level
  and the electrons at this level are called
  valence electrons

7
1st Level- holds 2 electrons
2nd level- holds 8 electrons
3rd level- holds 8
electrons (up to 18 in very large
atoms)
8
Valence Level the outermost electron level can
hold only 8 electrons. Valence Electrons are the
only electrons with a chance to escape the atom
9

• Chemical Symbol shorthand way to write an
  elements name- one or two letters (second letter
  not capitalized)
• Ex Na_______ Calcium____
• Al________ Gold____

10

• Some atoms of an element may have different
  numbers of neutrons.
• These atoms are called isotopes of the element

11

• Isotope Atoms of the same element that have the
  same number of protons, but a different number of
  neutrons