Basic Chemistry
CHAPTER 2-2
Radioisotopes
 Heavier isotopes that are unstable and tend to
decompose to become more stable
Radioactivity
 Radioactivity—process of spontaneous atomic decay
 What can we use this for?
Radioactivity
 But how does this happen?
Radioactivity
 But how does this happen?
 nuclei are unstable so dissipate excess energy by
emitting radiation in alpha, beta, or gamma rays
Radioactivity
 Radiometric Dating:
 Uranium

238U
to 206Pb, with a half-life of
4.47 billion years
 235U to 207Pb, with a half-life of
704 million years.
 Carbon
 Carbon-14 is a radioactive
isotope of carbon, with a halflife of 5,730 years
 Very short compared to other
isotopes
Radioactivity
 PhET Simulation
 https://phet.colorado.edu/en/simulation/beta-decay
Inert Elements
 Atoms are stable (inert) when the outermost shell is
complete
Inert Elements
 Atoms are stable (inert) when the outermost shell is
complete
 Atoms will gain, lose, or share electrons to complete
their outermost orbitals and reach a stable state
Inert Elements
 Atoms are stable (inert) when the outermost shell is
complete
 Atoms will gain, lose, or share electrons to complete
their outermost orbitals and reach a stable state
 Atoms are considered stable when their outermost
orbital has 8 electrons (With exception to the first
shell
Inert Elements
Reactive Elements
 Valence shells are not full and are unstable
 Tend to gain, lose, or share electrons
 Allow for bond formation, which produces stable
valence
Molecules and Compounds
 Molecule: Two or more like atoms combined chemically
 Compound: Two or more different atoms combined chemically
Molecules and Compounds
https://phet.colorado.edu/en/simulation/build-a-molecule
What are chemical reactions?
What do you remember?
What are chemical reactions?
 Atoms are united by chemical bonds
OR
 Atoms dissociate from other atoms when chemical
bonds are broken
Chemical Bonds
Ionic vs. Covalent
https://www.youtube.com/watch?v=fH
GSSV466Gk
Ionic Bonds
 Form when electrons are completely transferred
from one atom to another
 Ions
 Charged particles
 Anions - negative
 Cations - positive
 Either donate or accept electrons
Ionic Bonds
Na
Cl
Sodium atom (Na)
(11p+; 12n0; 11e–)
Chlorine atom (Cl)
(17p+; 18n0; 17e–)
+
–
Na
Cl
Sodium ion (Na+)
Chloride ion (Cl–)
Sodium chloride (NaCl)
Covalent Bonds
 Atoms become stable through shared electrons
 Single covalent bonds share one pair of
electrons
 Double covalent bonds share two pairs of
electrons
Covalent Bonds - Example
Covalent Bonds - Example
Covalent Bonds - Example
Covalent vs. Ionic bonds
https://phet.colorado.edu/en/simulation/sugar-and-salt-solutions
Covalent vs. Ionic bonds
• https://www.youtube.com/watch?v=mHKGLawOTww
• https://www.youtube.com/watch?v=9WXTbkBGPrE
• https://www.youtube.com/watch?v=dD0Xl4acUFg
Polarity
Covalently bonded molecules
Polarity
 Some are non-polar
 Electrically neutral
as a molecule
 Some are polar
 Have a positive and
negative side
Polarity
https://phet.colorado.edu/en/simulation/mol
ecule-polarity
Hydrogen bonds
 Weak chemical bonds
 Hydrogen is attracted to the negative portion of
polar molecule
 Provides attraction between molecules
Hydrogen bonds
Hydrogen bonds
 How many drops of water can you fit on a
penny?
 Who can guess correctly??