What is an Atom?
• Atom: Smallest unit
of all matter
• 3 Main Parts:
– 1) Proton (+)
– 2) Neutron (0)
– 3) Electron (-)
• Protons & Electrons
usually equal in
number
• Elements (substance
made of only 1 type of
atom) are identified
on the Periodic Table
Reading the Periodic Table
• Atomic Number: Number
of protons the atom
contains
– Usually # of electrons also
• Atomic Mass: Combined
# of protons and neutrons
inside the nucleus
– Electrons too small to affect
mass
Reading the Periodic Table
• Atomic Number: Number • How many protons,
of protons the atom
electrons, and neutrons
contains
does Carbon contain?
– Usually # of electrons also
• Atomic Mass: Combined
# of protons and neutrons
inside the nucleus
– Electrons too small to affect
mass
Protons = ______
Electrons = ______
Neutrons = ______
Reading the Periodic Table
• Atomic Number: Number • How many protons,
of protons the atom
electrons, and neutrons
contains
does Carbon contain?
– Usually # of electrons also
• Atomic Mass: Combined
# of protons and neutrons
inside the nucleus
– Electrons too small to affect
mass
Protons = ______
Electrons = ______
Neutrons = ______
Reading the Periodic Table
Protons
6 + Neutrons
+ Neutrons
= 12
= 12
• Atomic Number: Number • How many protons,
of protons the atom
electrons, and neutrons
contains
does Carbon contain?
– Usually # of electrons also
• Atomic Mass: Combined
# of protons and neutrons
inside the nucleus
– Electrons too small to affect
mass
Protons = ______
Electrons = ______
Neutrons = ______
What’s the:
A) Atomic number of
Beryllium?
4
Atomic number =
Atomic mass =
Atomic number =
protons usually
amount of protons
amount of protons
same as electrons
+ neutrons
B) Atomic mass of Beryllium?
9
C) How many protons?
4
D) How many electrons?
4
E) How many neutrons?
5
• Electrons orbit the nucleus
in “energy levels”
1st level:
• closest to nucleus
• stable w/ 2 electrons
• Electrons orbit the nucleus
in “energy levels”
1st level:
• closest to nucleus
• stable w/ 2 electrons
2nd level:
• stable w/ 8 electrons
7
1
8
6
5
1
2
4
2
3
• Electrons orbit the nucleus
in “energy levels”
1st level:
• closest to nucleus
• stable w/ 2 electrons
2nd level:
• stable w/ 8 electrons
Examine Carbon. It has 2 electrons in the first level and 4 electrons
in the 2nd level. Is Carbon stable?
• Electrons orbit the nucleus
in “energy levels”
1st level:
• closest to nucleus
• stable w/ 2 electrons
2nd level:
• stable w/ 8 electrons
3rd level:
• stable w/ 8 electrons
• Atoms are stable when the
outermost level is “full”
7
8
8
1
7
6
1
6
1
5
5
2
2
2
3
3
4
4
• Molecule: 2 or more atoms held
together by a covalent bond
– Form when atoms are
8 protons
unstable
• Covalent Bond: Chemical bond
where atoms share electrons
– Ex: Oxygen (O2)
8 electrons
• Why unstable? Only 6
electrons in outer energy level
6
1
1
5
2
4
2
3
• Molecule: 2 or more atoms held
together by a covalent bond
– Form when atoms are
unstable
• Covalent Bond: Chemical bond
where atoms share electrons
– Ex: Oxygen (O2)
• Why unstable? Only 6
electrons in outer energy level
• What happens? Oxygen atom
will share two electrons with
neighboring oxygen atom
• End result? Both end with 8
electrons in outer level (stable)
sodium
chlorine
• Defined: chemical bond where electrons are gained/lost
– Creates Ions (atoms with + or – charge)
• Held together by magnetic attraction
• Cause: 1 atom steals an electron(s) from another atom
• Ex: Sodium + Chlorine = Sodium Chloride
ee
e
Unstable
Stable
e
e
e
e
e
ee
ee
ee
e ee
e
ee
ee
e
Unstable
Stable
Before
After bonding
Na
Cl
Protons
(+)
11+
17+
Electrons
(-)
1110-
1718-
Net
charge
+1
0
-1
0
chlorine
sodium
ee
ee
e
ee
e
Unstable
Stable
e
e
e
e
e
ee
e
ee
ee
e ee
e
ee
ee
After bonding
Before bonding
Na
Unstable
Stable
Cl
Protons
(+)
11+
17+
Electrons
(-)
11-
17-
Protons
(+)
Electrons
(-)
0
Net
charge
Net
charge
0
chlorine
sodium
ee
ee
e
Na
Cl
11+
17+
10-
18-
+1
-1
Review
1) Name the 3 subatomic particles.
2) Which subatomic particles are found inside the
nucleus?
3) The atomic number usually allows us to determine the
amount of which two subatomic particles?
4) If an atom has the atomic mass of 14 and the atomic
number of 6, how many protons, neutrons, and
electrons does the atom contain?
5) After an ionic bond is formed, what is the charge of
the atom that gained an electron?
6) Which type of chemical bond shares electrons?