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Learning Goal: Today, we will identify the number of protons, neutrons and electrons for a given element.
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Journal #201. Who discovered the electron?2. What did Rutherford discover?
Atomic Structure
Learning Goal:Today, we will identify the number of protons,
neutrons and electrons for a given element.
AtomsElements consist of atoms.An atom is the smallest unit of an element
that has the chemical properties of that element.
Atomic Structure Even though elements are very tiny, they are
made up of smaller parts called subatomic particles.
There are 3 kinds of subatomic particles:Protons- positive chargeNeutrons-no chargeElectrons-negative charge
The NucleusThe nucleus is the small region in the center
of an atom.The nucleus has a positive charge because it
contains only protons and neutrons.
The Electron CloudElectrons move around the nucleus in a space
called the electron cloud.
Atomic NumberThe atomic number is equal to the number of
protons in an atom.Example:
Carbon has an atomic number of 6. That means it has 6 protons
Elements on the periodic table are ordered according to their atomic number.
Number of electronsFor all neutrally charged elements, the
number of protons equals the number of electrons:
Example:Oxygen has an atomic number of 8.
8 protons8 electrons
Atomic MassThe atomic mass is equal to # of protons + #
neutrons.Example:
Carbon has an atomic mass of 12 and an atomic number of 6. Therefore :
12(mass)-6(protons)= 6 neutrons
IsotopesAlthough all atoms of a given element contain
the same number of protons, the number of neutrons may differ.
Isotopes are named according to their atomic mass
Example:Most helium atoms have 2 neutrons, some
helium atoms only have one neutron.
Let’s Practice:1. For the element Oxygen: identify the
number of protons, neutrons and electrons.2. For the element Carbon-13: identify the
number of protons, neutrons and electrons3. For the element Hydrogen- identify the
number of protons, neutrons and electrons