Transcript Atoms, Ions, and Isotopes PowerPoint

Atoms, Ions, and Molecules
Think about it…
• What do a frog, a skyscraper, a car, and your
body all have in common?
ATOMS!
• Every physical thing you can think of, living or
not, is made of incredibly small particles called
atoms.
The atom
• The small basic unit of _____________.
– Matter – anything that takes
up space and has mass
• How small is an atom??
– Millions and millions of atoms could fit in the space
the size of the period at the end of this sentence.
Atoms consist of three types of smaller
particles:
• Protons (+)
• Neutrons (neutral)
• Electrons (-)
• Notice the location
of protons, neutrons,
and electrons in an atom
Element
• Element – type of atom that can’t be broken
down into a simpler substance
• Examples of elements:
– Hydrogen
– Lithium
– Carbon
– Boron
How do we identify an element?
Answer = by the number of protons
Atomic Number =
number of protons
Think about it: if Krypton loses a proton, is it still
Krypton??
• How can we identify the number of:
• Protons = ____________
• Neutrons = ___________
• Electrons = ___________
• From this picture?
Atomic Number =
number of protons
**Number of protons
and electrons is the
same
Atomic Weight
To find the number of neutrons you have to find the mass number.
To find the mass number, all you need to do is round the atomic
weight to the nearest whole number. In our example, krypton's
mass number is 84 since its atomic weight, 83.80, rounds up to 84.
THEN complete the formula below:
Mass Number = (Number of Protons) + (Number of Neutrons)
84 =
(36)
+
(??)
Elements
What four elements make up 96% of a human’s
body mass??
1.)
2.)
3.)
4.)
Elements
What four elements make up 96% of a human’s
body mass??
1.) Carbon
2.) Oxygen
3.) Nitrogen
4.) Hydrogen
Review
– Where are protons and neutrons found in the
atom?
– Where are the electrons found in the atom?
The Bohr Model
• Niels Bohr introduced “The Bohr Model” in 1913
• Model that shows the atoms electrons located
outside the nucleus in regions called energy levels
(valence shell)
Energy levels
The Bohr Model
• The first energy level can ONLY have up to 2
electrons
• The remaining energy levels can have up to 8
Energy level
Practice
• Draw a Bohr model of an oxygen and calcium
carbon atom.
Figure 2.3 Electron configurations-overview
Isotope – same number of protons (same
element) different number of neutrons
(different mass)
Example: Carbon 12, Carbon 13, Carbon 14
Figure 2.2 Nuclei of the three naturally occurring isotopes of carbon-overview
When atoms gain or lose electrons
• Ions – an atom that gained or lost one or
more electrons is called an ion
• Why do atoms gain or lose electrons?
– Atoms want a full outermost energy level (valence
shell)
– When an atom loses or gains electrons it has an
electrical charge (positive or negative)
For example:
• Sodium (Na) has how many electrons?
• Chlorine (Cl) has how many electrons?
Draw the Bohr model for each
Who is closer to having a full outermost electron
shell??
• Na will give one of its electrons to chlorine
– Becomes Na+ = positive charge = cation
• Cl will gain an electron from Na
– Becomes Cl- = negative charge = anion
Why are Ions important?
• Hydrogen ions (H+) are needed for the
production of usable chemical energy in cells
• Calcium ions (Ca2+) are necessary for every
muscle movement in your body
• Chloride ions (Cl-) are important for sending
chemical signals to your brain
Ionic Bonds
• Forms through the electrical force between
oppositely charged ions
• Think back to NaCl that we just talked about
Ionic Bond
•
•
•
•
Have you ever heard positive and negative attract?
It’s the same here!
Na+ attracts to ClNaCl = table salt
The positive sodium ion (Na+) and negative chloride
ion (Cl-) attract to each other and form an ionic bond
BUT, Not all atoms easily gain or lose
electrons…
• It is possible for atoms to share electrons
• A covalent bond forms when atoms share a
pair of electrons
• Draw a Bohr model for oxygen and carbon
– How many electrons does oxygen need to fill its
outermost shell?
– How many electrons does carbon need to fill its
outermost shell?
Carbon dioxide (CO2) is a covalent
bond
• An oxygen atom needs two electrons to fill its
outer energy level. A carbon atom needs 4
electrons to fill its outer energy level. In carbon
dioxide, carbon makes a double bond, or SHARES
two pairs of electrons with each oxygen atom
Water (H2O) is a covalent bond
What is a molecule?
• Molecule- two or more atoms held together
by covalent bonds
For example: H2O, CO2, O2, etc.
**Almost all of the substances that make up
organisms are molecules held together by
covalent bonds
Compounds
• A substance made of different elements
bonded together in a certain ratio
• Held together by chemical bonds
• H2O, CO2, NaCl….can you think of any others?