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UNIT 2 – THE ATOM
The simplest form of matter is the element. The smallest particle of
matter is an ATOM. It is called the building block of matter.
Element is the name given to the physical thing the atom.
Separate the following into organized groups.
They are all circles and have the same shape. However, they are different sizes
and patterns. Once they are grouped, it would be easier to give them a name
to help identify them. The name given is what we know as the element name.
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Atoms of the same element are the same.
Atoms of different elements are different.
Atoms are made up of 3 subatomic particles.
- Protons
- Neutrons
- Electrons
PROPERTIES OF SUBATOMIC PARTICLES
A. LOCATION
Protons and neutrons are clumped together to form the Nucleus.
Electrons are always moving outside the nucleus in the area known as the
Electron Cloud.
B. CHARGES
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Protons have a +1 charge.
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Neutrons have no charge (0).
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Electrons have a –1 charge.
*So, the nucleus is always positively charged since only neutral and positively
charged particles are in it.
C. MASS
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Protons have a mass of 1 amu or atomic mass unit.
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Neutrons have a mass of 1 amu.
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Electrons have no mass. It is actually 1/2000 of an amu which is so
small that it is considered 0.
PROPERTIES OF THE ATOM
A. ATOMIC NUMBER
The atomic number of an atom is an extremely important fact about the
atom. The atomic number is equal to the number of protons in the atom.
This number can be looked up on the Periodic Table and tell us what
element the atom is. The element is determined by how many protons
the atom has. If the number of protons changes, then the element
changes.
ATOMIC NUMBER = # of protons
which tells you the ELEMENT
B. CHARGE
The atom’s charge is based on the protons and the electrons. You can
determine the atom’s charge using the following equation.
CHARGE = (# of protons) – (# of electrons)
C. MASS NUMBER
All the mass of the atom is in the nucleus since that is where the protons
and neutrons are and they are the only particles that have mass. You
can determine the atom’s mass using the following equation.
MASS OF ATOM = (# of protons) + (# of neutrons) AMU
D. ATOMIC MASS
This is the average of all mass numbers of the element with respect to
their frequency in nature. This value is found on the Periodic Table once
we know what element the atom is.
How to write the symbols of the atom:
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Write the symbol of the element. If the atom has a charge, it must
be written with a positive or a negative and the number of the
charge as a superscript behind the symbol. If there is no charge on
the atom, then just write the symbol.
Examples:
Zn+2, Se-2, Cr, F-1, H+1, Al+3
ISOTOPES
Isotopes are atoms of the same element but have different mass
numbers. Since they are the same element, they have the same number of
protons. But their mass numbers are different so that means it is because of a
different number of neutrons.
How to write the symbols of an isotope:
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Write the symbol of the element.
The mass number of that particular isotope is written as a
superscript in front of the symbol.
The atomic number of the element is written as a subscript in front
of the element.
Examples:
12
6
C,
13
6
C,
1
1
H,
2
1
H,
3
1
H