An atom is the smallest particle of an element that retains
the chemical identity of the element.
Three Parts of Atom
Particle
Proton
Neutron
Electron
Charge
+1
0
-1
Mass
1.67x 10-24 g
1.67x 10-24 g
9.11x 10-28 g
Atomic mass units
1 amu
1 amu
0 amu
Where are they?
•
•
•
•
Nucleus is made up of protons and neutrons.
Electrons move around the nucleus.
Mass is concentrated in the nucleus.
99.97% of the mass is in the nucleus.
How big are atoms?
• If nucleus is size of a golf ball, the electrons
are how far away?
•
1 mile! Lots of empty space
• How big are they?
• 6.02 x 1023 atoms in 12 grams of carbon.
How many protons?
• The atomic number is the number of protons
in the nucleus of the atom.
Look at the periodic table for this.
The number of protons identifies the element.
How many neutrons?
• The number of neutrons may vary.
• An isotope is an atom that has the same number of
protons as other atoms of the same element, but
different number of neutrons.
• Same atomic number = same element
• Protons + Neutrons = Atomic Mass
• Isotopes have different atomic masses, because they
have different number of neutrons.
A
NEUTRON
WALKED INTO A BAR AND ASKED…
HOW MUCH FOR A ROOT
BEER?
THE BARTENDER SAID
FOR YOU, BUDDY…
NO CHARGE!
How many electrons?
• The number of electrons equals the number
of protons in a neutral atom
• An ion is a charged atom in which the number
of electrons can increase or decrease.
• More electrons than protons, charge is
negative
• Fewer electrons than protons, charge is
positive
CARBON
Carbon has
• 6 protons
• 6 neutrons
• 6 electrons
6 amu
6 amu
0 amu
• Total atomic mass = 12 amu
How do we write this?
• Carbon-12
• C-12
• 12C
• 12 6 C0
• The periodic table tells us that carbon has 6 protons.
• The mass is 12 amu and equals protons plus
neutrons, so it has 6 neutrons.
• It is neutral (has no charge), so it has 6 electrons.
Isotope of carbon
• Carbon-14
• C-14
• 14C
• 14 6 C0
• The periodic table tells us that carbon has 6 protons.
• The mass is 14 amu and equals protons plus
neutrons, so it has 8 neutrons.
• It is neutral (has no charge), so it has 6 electrons.
Carbon-14 isotope said
to Carbon-12 isotope,
“Does these neutrons
make my mass look big?
What’s the
safe answer
here?
???
Ion of carbon
• Carbon-12
• C-12
• 12C
• 12 6 C+4
• The periodic table tells us that carbon has 6 protons.
• The mass is 12 amu and equals protons plus
neutrons, so it has 6 neutrons.
• It is positive (it lost 4 electrons), so it has only 2
electrons.
OH NO!!!
I think LOST an
ELECTRON!!
Are you
POSITIVE?
A
n (- or +)
E
Z
E = element symbol
Z = atomic number = # protons (identifies element)
A = atomic mass = # protons + # neutrons
n = charge
(+ if fewer electrons than protons)
(- if more electrons than protons)
What is the name of the element that has…
• 5 protons
• 17 protons
• 25 protons
• 82 protons
• 92 protons
What is the chemical symbol of…
The atom with
• 8 protons
• 11 protons
• 9 protons
How many protons and electrons in atoms
of…?
• vanadium?
• nitrogen?
• argon?
• potassium?
What is the chemical symbol of…
The ion with
• 8 protons and 10 electrons
• 11 protons and 10 electrons
• 9 protons and 10 electrons
Write the chemical symbol for the ion
with…
• 12 protons and 10 electrons
• 74 protons and 68 electrons
• 95 protons and 89 electrons
Write the chemical symbol for the ion
with…
• 33 protons and 36 electrons
• 29 protons and 27 electrons
Write the chemical symbol for the atom
with…
• 5 protons and 6 neutrons
• 13 protons and 14 neutrons
• 8 protons and 8 neutrons
Show 3 ways to write
• The atom with 53 protons and atomic mass 131
How many neutrons are in this isotope?
How many protons, neutrons , electrons…
59
2+
Ni
28
How many protons, neutrons , electrons…
91
4+
Zr
40
How many protons, neutrons , electrons…
140
3+
Ce
58
How many protons, neutrons , electrons…
79
Se
34
2-
How many protons, neutrons , electrons…
45
Sc
21
3+
How many protons, neutrons , electrons…
13
4-
C
6
Write the complete chemical symbol for
the ion with…
84 p
125 n
80 e
Write the complete chemical symbol for
the ion with…
27 p
32 n
25 e
Write the complete chemical symbol for
the ion with…
73 p
108 n
68 e
Write the complete chemical symbol for
the ion with…
31 p
39 n
28 e