Transcript Chemistry

Atoms to Molecules
Atomic Size
• Atoms are unbelievably tiny. How tiny?
Incredibly smaller than plant and animal
cells. Billions of atoms make up the writing
tip of your pen or pencil.
Atom Characteristics
• All matter (stuff with mass and volume) is
made of atoms.
• Space (without any particles) has no atoms.
• Atoms are made of smaller particles :
protons (+), neutrons ( ), and electrons (-).
• Protons, neutrons, and electrons, of course,
are made of even smaller particles…
Sub-subatomic
particles
• Protons, electrons and neutrons are
made of even smaller particles
including,
• Quarks, bosons, fermions, mesons, and so
on.
• Particle physics studies these entities.
Protons
• Positvely charged
• Equals the atomic number of an
atom.
• Always stays the same for an
element.
• Located in the nucleus of the atom.
Neutrons
• Neutral charge
• Atonmic mass minus the atomic
number equals the number of
neutrons.
• Different isotopes have different
numbers of neutrons.
• Always in the nucleus.
Electrons
• Negative electrical charge
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Electrons equal protons in atoms.
Missing electrons make positive ions.
Extra electrons make negative ions.
Located in shells outside nucleus.
Radioactivity
• Most elements give off neutrons or
protons spontaneously into space at high
speeds.
• Alpha Particle = 2 protons and 2 neutrons
• Beta Particle = electron
• Gamma Ray = electromagnetic wave.
• All three types of radiation are ionizing
(dislodge electrons and cause chemical
reactions to happen)
Radiation Types
Ions
• When an atom loses or gains an
electron, it is called an ion. Ions
attract oppositely charged ions.
• For example, sodium has 11
protons and 11 electrons. When
it loses an electron, it becomes
+1
an ion with a +1 charge, Na
Other Ions
• Chlorine has 17 protons and 17 electrons.
When it steals sodium’s electron, it will
have 18 electrons, and becomes an ion with
a –1 charge. Cl-1
• Na+1 Cl-1
• Sodium and chlorine bond to each other to
become a molecule of sodium chloride.
Molecules
• Like sodium chloride, a molecule is any two
atoms which bond together. Other examples
H2O, CO2,
and O2
include
Molecules
• There are two types of
bonding. Ionic bonding
occurs with a metal and a
nonmetal. Covalent
bonding occurs when two
nonmetals bond together.
Bonding
• Ionic bonds have stronger forces
holding them together, so they
result in higher boiling points.
• Covalent bonds share electrons.
They are weaker bonds than ionic
forces and covalent compounds
have lower boiling points.
H2O – with covalent bonds
Ionic Bonds
• NaCl
• CaCl2
The End