chem chapter 1 Periodic Table and Modern Theory Summary

The Periodic Table

• The periodic table contains 92 elements (first 92).

• Elements with atomic numbers greater than 92 are synthetic.

• About 90 elements are found in nature.

• Some synthetic elements above uranium are radioactive and decay.

Modern Theory of the Universe: The Big Bang

• Approximately 14 billion years ago, the Big Bang is theorized to have occurred from a singularity.

• The Big Bang was an explosion of matter that expanded outward.

• Gravity caused gases to attract each other.

• Hydrogen condensed, releasing heat and forming stars.

• Stars are fusion reactors, converting hydrogen and creating elements up to iron (element 26).

Stellar Evolution and Element Formation

• Stars burn out and explode as supernovas.

• Supernovas create heavier elements and disperse them into the universe.

• Gravity pulls the dispersed elements together, forming new stars and planets.

• About 4 billion years ago, a cloud of gas condensed to form the sun and planets.h

• Heavier elements sank towards the center of planets, forming iron and nickel cores.

• Lighter elements like oxygen and silicon formed the Earth's crust.

• Hydrogen reacted with oxygen to form water ($H_2O$).

Origin of Life and Composition of Living Organisms

• Life is believed to have formed in water (lakes or oceans) due to faster chemical reactions in liquids.

• Living organisms are approximately 85% water.

• After removing water, organisms are primarily carbon.

• Carbon can form chains known as polymers, essential for sugars, proteins, starches, and cellulose.

• The elements that compose us come from exploding stars.

Chemical Symbols and Nomenclature

• Element symbols: Single letter symbols are capitalized (e.g., H for hydrogen). Two-letter symbols have the first letter capitalized and the second lowercase (e.g., He for Helium).

• $CO$ represents carbon monoxide, a poisonous gas. $Co$ represents cobalt.

• Some symbols are derived from Latin names (e.g., Na for sodium from natrium, K for potassium).

• Examples of symbols from Latin names:

  • Na (sodium) - natrium

  • K (potassium)

  • Cu (copper) - cuprum

  • Pb (lead) - plumbum

  • Hg (mercury)

• Placeholder elements (Unun…) are named by the International Union of Pure and Applied Chemistry (IUPAC) after verification.

• Americium (Am) was named after America, Curium (Cm) was named after Marie Curie and elements where named after scientists like Einsteinium, Fermium and Lawrence.

• During the Cold War, naming new elements was delayed due to tensions between the US and the Soviet Union.

Molecular Composition

• Atoms can combine to form molecules (e.g., two oxygen atoms form $O_2$).

• Allotropes: Different forms of the same element (e.g., $O<em>2$ and $O</em>3$ (ozone)).

• Sulfur forms molecules with eight sulfur atoms ($S_8$).

• Fullerene is a form of carbon with 60 carbon atoms in a spherical molecule.

• Homoatomic molecules consist of one type of element; heteroatomic molecules consist of multiple elements (e.g. $H_2O$).

Atomic Composition

• Monoatomic: Single atom.

• Diatomic: Two atoms.

• Triatomic: Three atoms.

• Tetraatomic: Four atoms.

• Pentatomic: Five atoms.

• Example: $Mn(NO<em>3)</em>2$ (manganese(II) nitrate)

  • Contains one manganese atom.

  • Two nitrate groups (NO3).

  • Total atoms: 1 Mn + 2 N + 6 O = 9 atoms.

  • Within each $NO<em>3$ there are 3 Oxygens so for $Mn(NO</em>3)_2$ the amount of Oxygen would be 6

• Example: $(NH<em>4)</em>2SO_4$ (ammonium sulfate)

  • Number of atoms: (1 N + 4 H) * 2 + 1 S + 4 O = 2 N + 8 H + 1 S + 4 O = 15 total atoms.

Chemical Formulas

• Chemical formulas, such as $H_2O$, provide limited information.

• More complex representations can show molecular geometry

• Example structure of $CH_4$ (methane) is tetrahedral, not flat.

Carbon chains

• Carbon atoms form chains bonded to other elements forming variety of compounds

• Ethanol (alcohol). Formula: $C<em>2H</em>5OH$

• Dimethyl ether (ether). Formula: $CH<em>3OCH</em>3$

Assignment and Categorizations

• Molecules containing three kinds of atoms are classified as compounds.

• Homoatomic molecules are elements.

• Molecules are both heteroatomic and triatomic: compound

True or False questions

• A molecule of an element may be homoatomic or heteroatomic depending on which element is involved. False: A molecule of an element may only be homoatomic. This can be a pure element Carbon.

• The limit of chemical subdivision for a compound is a molecule. True.

• Only one kind of atom may be present in a homoatomic