Lecture Notes Flashcards

Chemistry Basics

• Density:
  • Definition: Mass per unit volume.
  • Water: 1 \frac{g}{mL}
  • Gold: 18 \frac{g}{mL}
• Atoms:
  • Protons: Positive particles in the nucleus.
  • Neutrons: Neutral particles in the nucleus.
  • Electrons: Negative particles orbiting the nucleus.

Periodic Table

• Atomic Number:
  • Definition: Number of protons in an atom's nucleus.
  • Unique identifier for each element.
• Electrons in a Neutral Atom:
  • Number of electrons equals the number of protons.
  • Ions: Atoms that have gained or lost electrons, resulting in a net charge.
• Changing Atoms:
  • Changing the number of protons changes the atom's identity (nuclear reaction).
  • Example: Removing a proton from carbon turns it into boron.
• Atomic Mass:
  • Calculation: Sum of protons and neutrons in the nucleus (electrons have negligible mass).
  • Measured in Daltons (atomic weight units).
  • Example:
    • Helium: 2 protons + 2 neutrons = atomic mass of 4.
    • Oxygen: 8 protons + 8 neutrons = atomic mass of 16.

Valence Electrons and Valences

• Valence Shell:
  • Outer electron shell.
• Valence Electrons:
  • Electrons in the outermost shell.
  • Example: Nitrogen has 5 valence electrons.
• Valences:
  • Unpaired electrons in the outer shell.
  • Represent the number of spaces available for bonding.
  • Example: Nitrogen has 3 valences (unpaired electrons).

Electron Arrangement and Energy Shells

• Energy Shells (Orbitals):
  • Regions where electrons move.
  • First shell: 2 electrons.
  • Second shell: 8 electrons.
  • Third shell: 8 electrons.
• Electron Attraction:
  • Electrons are attracted to the positively charged nucleus.
• Lithium Example:
  • Lithium has 3 protons and 3 electrons.
  • The first shell accommodates 2 electrons, and the third electron goes into the next shell.
  • It has seven available spaces left.
• Boron Example:
  • Boron has 5 protons, therefore five electrons will be present.
  • 2 electrons go into the first shell, and 3 electrons occupy the outter shell.

Covalent Bonds

• Covalent Bond Formation
  • Atoms like carbon, nitrogen, and oxygen (with 4, 3, and 2 spaces, respectively) tend to form covalent bonds.
  • The number of spaces in the outer shell often equates to the number of covalent bonds an atom can form.
• Inert Atoms (Noble Gases)
  • Helium, neon, and argon have full outer shells and are nonreactive.
• Reactivity
  • Atoms with spaces in the outer shell are reactive and undergo chemical reactions to fill those spaces.
  • Lithium tends to lose its outer electron to achieve a full outer shell.

Ions: Cations and Anions

• Ions Definition:
  • Atoms with a different number of electrons than protons.
• Lithium Example:
  • Lithium loses an electron, resulting in one extra positive charge and forming an ion.
• Sodium and Chlorine Example:
  • Sodium readily loses its outer electron; chlorine readily gains one to complete it's own outer shell.
• Stability:
  • Atoms are more stable with a filled outer shell.
• Cations:
  • Ions with a positive charge.
• Anions:
  • Ions with a negative charge.

Isotopes and Atomic Weight

• Isotopes:
  • Atoms with the same number of protons but different numbers of neutrons.
  • Example: Carbon-13 (carbon with an atomic weight of 13).
• Neutron Calculation:
  • Subtract the number of protons from the atomic weight.
  • Example:
    • Carbon-13 (6 protons): 13 - 6 = 7 neutrons.
    • Neon-21 (10 protons): 21 - 10 = 11 neutrons.
• Atomic Mass:
  • Explains why atomic weights are not exact numbers.
  • Represents the average weight of all isotopes of an element.

Carbon-14 Dating

• Process:
  • Determines the age of dead organisms by measuring the decay of carbon-14.
• Half-Life:
  • Carbon-14 decays into nitrogen with a half-life of 5,730 years.
  • Half-life: Time for half of a quantity of an isotope to decay.

Chemical Bonds: Covalent, Ionic, and Hydrogen

• Covalent Bonds
  • Involve the sharing of electrons between atoms.
  • Important for forming molecules like fats, DNA, RNA, and proteins.
  • The number of spaces in the outer shell indicates how many covalent bonds an atom can form.
• Ionic Bonds
  • Result from the attraction between oppositely charged ions.
• Hydrogen Bonds
  • Important for DNA structure and water's properties.

Covalent Bonds in Detail

• Sharing Electrons:
  • Atoms share electrons to fill their outer shells.
• Hydrogen Example:
  • Two hydrogen atoms share electrons to fill each other's space.
• Oxygen Example
  • 2 unfilled spaces in the outer shell leads to 2 covalent bonds.

Ionic Bonds in Detail

• Formation:
  • Involve the attraction between a cation and an anion.
• Salt Formation:
  • Substances formed via ionic bonds are called salts.
  • Examples A calcium, magnesium or potassium salt will be the element stuck to an anion.
• Acids and Bases
  • If the cation is a Hydrogen ion, the salt is acidic.
  • If the anion is Hydroxide, the salt is basic.

Acids and Bases

• Definition:
  • Solutions with more hydrogen ions than hydroxide ions are acids.
  • Solutions with more hydroxide ions than hydrogen ions are bases (alkaline).
  • Neutral solutions have equal amounts of both.
• pH Scale:
  • Used to measure acidity or alkalinity.
  • pH 7 is neutral (pure water).
  • pH < 7 is acidic (more hydrogen ions).
  • pH > 7 is alkaline (more hydroxide ions).