Download What is an atom?

ATOMIC STRUCTURE
What is an atom? What is the
structure of an atom? How is an
atom different from an element?
How is it different from
compound?
Definition:
• An atom is the smallest
particle of matter that still
retains the property of that
substance.
• It is the basic unit of
matter, much the cell is the
basic unit of all living
things.
Structure: a small, dense nucleus surrounded
by orbiting electrons.
Subatomic Particles:
(particles that make up atoms)
Three types of particles:
PROTONS
NEUTRONS
ELECTRONS
PROTONS
• Positively charged particles
• Located in the nucleus of the
atom
• Contribute to the mass of the
atom
Neutrons
• Have no charge.
• Located in the nucleus of the
atom.
• Contribute to the mass of the
atom.
Electrons
• Have a negative charge
• Located outside of the nucleus
• Do NOT contribute to the
mass of the atom
Wait….so let me get this
straight…..
Particle
Location
Charge
Mass
Proton
Nucleus
Positive
1 amu
Neutron
Nucleus
Neutral
1 amu
Electron
Outside
Nucleus
Negative
None
The whole picture…
What is an element???
• An element is a substance made up of
one type of atom.
• Example: gold, tin, oxygen
(anything on the periodic table)
So….
• Atoms make up elements.
• All atoms of the same element are alike,
and different from atoms of other
elements.
– For example, all gold atoms are the same, but
different from oxygen atoms.
Atomic Number…
• The atomic number is the
number of protons in an atom.
• Each type of atom has a
different number of protons.
Atomic Number
Atomic
Number
All atoms of lead (Pb) have 82 protons.
Atomic Mass
• Atomic Mass or Mass Number—number
of protons plus neutrons.
atomic mass = # protons + # neutrons
# neutrons = atomic mass - # protons
# protons = atomic mass - # neutrons
Let’s Try this…
• How many protons are in an atom of
Carbon?
6 protons
• How many protons in an atom of
Hydrogen?
1 proton
Now let’s try mass….
• What is the mass of an atom containing 14
protons and 12 neutrons?
– 14 + 12 = 26 amu
• What is the mass of an atom containing 10
protons and 10 neutrons?
– 10 + 10 = 20 amu
• What is the mass of a sulfur atom
containing 15 neutrons?
- 15 + 16 (protons) = 31 amu
Another Example…
• What is the mass of an atom with 6
protons and 6 neutrons?
– What is the identity of this atom?
What is the mass of an atom with 6 protons and
7 neutrons?
What is the identity of this atom?
Isotopes
Two atoms of the same element with
different masses.
Example:
Carbon-12
Carbon-13
What is a compound??
• A compound is a substance composed of
two or more elements chemically bonded.
– Examples: water, carbon dioxide, baking soda
H2O
The Bottom Line…
• All atoms are made up of protons, neutrons and
electrons.
• All matter is made up of atoms.
• All elements are made up of atoms.
• All compounds are made up of elements.
What about electrons?
• Electrons are located outside the nucleus.
• They orbit the nucleus in a complex
pattern at different levels.
• The outermost electrons – those farthest
from the nucleus are called VALENCE
ELECTRONS
Here is the basic structure:
Valence
electrons
What is the identity of this atom?
What is the mass of this atom?
The formation of ions…
Neutral atom
Ion
Two valence
electrons are
lost
30 protons (zinc)
30 electrons
0
= neutral atom
30 protons (still zinc)
28 electrons
+ 2 charge
Try this….
• What is the charge of an ion with 24
protons and 26 electrons?
• -2
• What is the charge of an ion with 12
protons and 11 electrons?
+1