Objective
• On a note card or ½ sheet of paper please
write the following which you will give me
as your exit ticket
• Objective:
name the parts of an atom?
Matter and Atoms
• All matter is made of atoms!!!
• Atom: the smallest unit of an element that
maintains the properties of that element.
• Atoms are so tiny scientists need a very
powerful microscope to see them!
Atoms
• As tiny as an atom is, it is made up of even
smaller particles.
• Protons
• Neutrons
• Electrons
• 2 parts of an atom Nucleus and Electron
Cloud!
The Nucleus
• Protons are positively charged
particles in the nucleus.
• Neutrons are the particles of the
nucleus that have no electrical
charge.
Outside the Nucleus
• Electrons are the negatively charged
particles in atoms.
• Electrons are found around the
nucleus within electron clouds.
• Atomic Number the number of
protons in the nucleus. An atom has
the same number of protons as
electrons.
Picture of an Atom
Electron cloud
nucleus
Ions
• Its what an atom is called when there
protons and electrons are not equal.
• An atom that loses one or more electrons is
called a Positively Charged Ion.
• An atom that gains one or more electrons it
is called a Negatively Charged Ion.
Atomic Number
• There are more than 110 different
elements/atoms.
• Atomic Number:The number of protons in
the nucleus of an atom: the atomic number
is the same for all atoms of an element.
• Carbon has 6 protons in its nucleus, so its
atomic number is 6.
How do Atoms differ?
• Atoms make up individual elements. By
changing the number of protons in the
atom, you change the type of element.
• For example: The hydrogen atom has
1 proton and 1 electron.
• The helium atom has 2 protons, 2
neutrons, and 2 electrons.
• For bigger atoms, simply add protons,
neutrons, and electrons.
Isotopes
• Isotopes are atoms that have the
same number of protons but have
different numbers of neutrons.
• You can identify each isotope of an
element by its mass number. The
mass number is the sum of the
protons and neutrons in an atom.
Atomic Mass
• Most elements contain a mixture or two or
more isotopes.
• The Atomic Mass: of an element is the
weighted average of the masses of all the
naturally occurring isotopes of that element.
How to find A.M.
• Multiply the mass numbers of each isotope by its
percentage in decimal format.
• So you have Chlorine-35 at 76% and Chlorine-37
at 24%.
• (35X0.76)=26.60
• (37X0.24)=8.88
• Then add the two answers together
• 26.60 + 8.88=35.48 amu