Week 1 - Basic Chemistry Review Flashcards
Compare and Contrast:
Solids, Liquids, Gases, Plasma
Solid: materials that resist changes in shape and volume
Liquid: fluid, not compressible, may change volume with changes in pressure/temp
Gases: fluid, compressible, easily change volume with changes in pressure/temp
Plasma: heated gas where electrons come loose
Describe the structure of an atom
Nucleus - central core (contains protons and neutrons) - protons determine what element it is
Electrons - orbiting particles (negatively charged) (determine the reactivity of the element)
Describe atomic structures of:
Hydrogen, Oxygen, Carbon, Nitrogen
Hydrogen (63%) - 1 valence electron
Oxygen (24.2%) - 6 valence electrons
Carbon (10.5%) - 4 valence electrons
Nitrogen (1.35%) - 5 valence electrons
“Rule of Eight” (Octet Rule)
Bonds are formed such that each atom is surrounded by a complete octet (8) of electrons (except hydrogen)
Molecules are more stable with 8 electrons in the outer shell
How much energy is required to remove an electron from the atom?
Electrons in the lowest energy level require the most energy to be removed from the atom
Electrons in the higher energy levels require less energy to be removed from the atom
What are Ionic Bonds?
Made by the attraction of electrons between atoms due to electron distribution - “opposites attract”
Atoms fill their outer shells by completely acquiring or losing electrons becoming ionized “+ or -“
Types: Ion-Ion, Ion-Dipole, Dipole-Dipole
Ex: Na loses outer electron to form cation (+) Cl gains electron to form anion (-) they attract to each other and form NaCl via ionic bond
What are Covalent Bonds?
The physical sharing of electrons between atoms
Can have single, double, or triple bonds
Stronger than ionic bonds
Ex: Carbon binding with 4 hydrogen
Saturated Hydrocarbons vs Unsaturated Hydrocarbons
Saturated: single-bonded (alkanes) carbon chains with all available carbon bonds attached to hydrogen
Unsaturated: double (alkenes) or even triple (alkynes) bonds between the carbon atoms
What are Ion-Ion Forces?
Ions of like charges repel one another and ions of unlike charges attract one another (“Opposites attract”)
Not Directional, occur anywhere along the outer shell
Lead to the formation of ionic solids at room temp - readily dissolve in water
High melting and boiling points
Ex: NaCl
What are Induced Dipole Forces?
Distribution of electrons in a nonpolar molecule can be distorted by a nearing electrical charge to induce a dipole
Weak and only effective at a short range
What are Ion-Dipole Forces?
Interaction of a polar molecule with both + and - ions
+ ions are attracted by the - end of the dipole and repelled by the + end and vice versa
Weaker than ion-ion
Requires a mixture of two or more substances: one to provide ions and another to provide polar molecules
Ex: interaction of water with dissolved ions
What are Dipole-Dipole Forces?
Attractive forces resulting from the interaction of polar molecules
Moderately strong but weaker than ion-ion
Attractions fall off more rapidly with distance than ion-ion forces
What is Hydrogen Bonding?
Special type of dipole-dipole attraction
Occurs when H+ covalently bound to a nitrogen, oxygen, or fluorine interacts with the lone pair of a second such atom nearby
Stronger than other dipole-dipole but weaker than covalent bonds
May be intermolecular or intramolecular
What are London Dispersion Forces?
A fluctuation of the electron distribution on one atom induces a corresponding temporary dipole moment on a neighboring atom – the two dipoles moments interact to give a net attractive force
Strength increases with the number of electrons in the atom (heavier atoms interact more strongly than lighter ones)
Ex: interaction with an inert gas
Intermolecular Forces of Attraction (strength of attraction related to escape of electrons)
The higher the strength of attraction is the harder it is for electrons to escape into gases thus increasing the boiling point
