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Basic ChemistryCHAPTER 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 half-life 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 ElementsValence shells are not full and are unstable
Tend to gain, lose, or share electronsAllow 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=fHGSSV466Gk
Ionic Bonds
Form when electrons are completely transferred from one atom to another
IonsCharged particles
Anions - negativeCations - positiveEither donate or accept electrons
Ionic Bonds
+ –
Sodium atom (Na)(11p+; 12n0; 11e–)
Chlorine atom (Cl)(17p+; 18n0; 17e–)
Sodium ion (Na+) Chloride ion (Cl–)
Sodium chloride (NaCl)
ClNaClNa
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-polarElectrically neutral
as a molecule
Some are polarHave a positive and
negative side
Polarity
https://phet.colorado.edu/en/simulation/molecule-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??