Chemistry is:
The Study of Matter
Objective:
Describe the
structure of atoms,
including the location
of protons, neutrons,
and electrons.
History


Greek philosopher Democritus around 1600 said
matter was composed of small particles called atoms
and that different types of matter where made of
different types of atoms.
English schoolteacher John Dalton around 1810 said:
1.
2.
3.
4.
Matter was made up of atoms
Atoms cannot be divided into smaller pieces
All atoms of an element are the same atom
Different elements mean different atoms are present
1.
Atoms:
2.
3.
4.
Basic building
blocks of matter
Have no charge
(neutral)
Tiny particles that
make up matter
Particles that
make up the
atom:
1.
2.
3.
Protons
Neutrons
Electrons
Definitions







Matter – anything that has mass and takes up space
Element – matter made up of one kind of atom
Compound – matter made of two or more different
atoms
Proton – positively charged particle inside the nucleus
of an atom
Neutron – neutral particle inside the nucleus; gives
atom extra mass
Electron – negatively charged particle
Electron cloud – region surrounding nucleus where
electrons travel
Atomic particles
Protons
Neutrons
Electrons
Same as:
Atomic
number
Location:
Nucleus
Neutrons +
---------------Protons =
atomic mass
Nucleus
Electron
cloud
Charge:
Positive
No Charge
Negative
Energy
Levels /
Orbitals:
----------------
----------------
1st = 2
2nd = 8
3rd = 18
Model of an Atom
negative
Negatively
charged
Positively charged
What kind of charge do atoms
have?
The atom is neutral because the charges
of the protons are balanced by the
negative charges of the electrons.
An atom of carbon has six protons and six
neutrons(maybe) in its nucleus.
How many electrons will it have?
What will be the atomic mass?
Part 2
Atom
contains
protons
positive
contains
contains
neutrons
Atomic
number
neutral
With protons give
Mass number
electrons
In electron negative
cloud
Definitions




Atomic number – number of protons in the nucleus of
an element. Atoms of an element are identified by the
atomic number because it never changes without
changing the identity of the element
Mass number – number of protons plus neutrons
Isotopes- atoms of an element with different numbers
of neutrons
Valence electrons- electrons in the outermost level
Symbols used for elements



The elements are on the
periodic table and are
abbreviated with one or
two letters
The first letter is always
capitalized
If a second letter is
present it will be a
lowercase letter

Examples:
–
–
–
–
–
H = hydrogen
Al = aluminum
Na = sodium
C = carbon
Hg = mercury
Calculating Neutrons


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Remember, protons and neutrons are in the
nucleus
Nucleus is what gives the atom its mass
Atomic number the same as proton number
Subtract atomic number from mass number to
get neutrons
Isotopes??



13 Protons 14 Neutrons 13 Electrons
13 Protons
16 Neutrons
13 Electrons
2 Protons 2 Neutrons 2 Electrons
3 Protons 3 Neutrons
3 Electrons
21 Protons 20 Neutrons 19 Electrons
21 Protons 18 Neutrons
21 Electrons
Valence Electrons



The group / family number determines the
number of valence electrons (outermost
electrons)
All elements in group 1 have 1 electron in their
outermost energy level.
All elements in group 14 have 4 electrons in
their outermost energy level.