Chapter 2 Flashcards
Atoms vs. Molecules
Molecule: two or more atoms held together by covalent bonds; multiple atoms held together by chemical bonds(like O2)
Atoms: smallest identifiable unit of matter that still has chemical properties
Elements vs Compounds
Element: all of one type of substance
Example: room full of just oxygen; even with oxygen as O2, still only one element in the room
Compound: more than one type of atom in a substance; dealing with a type of substance
Example: water being made up of two hydrogens and one oxygen
Example: carbon dioxide
Example: Ammonium
Parts of an atom
(Protons and electrons of elements are meant to cancel out to have an overall neutral state)
Nucleus: Inside, it has protons and neutrons, Can vary on each element and its isotopes as well
Protons: Determine type of element(atomic number)
Electrons: Multiple ways to be shown on a diagram; Can occupy different energy levels; Ideally the same number of protons(to balance the charge!!)
Neutrons: Contribute no charge
Atomic number and Atomic Mass/Mass Number
Atomic number determines element
Atomic number = number of protons
Mass number = number of protons + number of neutrons
Mass number – atomic number = number of neutrons
Isotopes
“multiple versions” of an element that differ in neutron number
Affects mass number
Can undergo radioactive decay: Decay at predictable rates, Helps with dating rock stratus age
Isotopes = diff. number of neutrons
Valence Electrons
Electrons in the outermost shell of the atom, called the “valence shell”; Can form chemical bonds when outermost shell is not full(?)
Valence of an atom: number of unpaired valence electrons
Full valence shell = chemically unreactive; Different atoms have different numbers of unpaired electrons
Octet Rule: a full 8 electrons, each atom must balance its need to fill the outermost shell with a need to balance charges
Types of chemical bonds
Ionic and covalent
Ionic Bonds
atoms EXCHANGE electrons in order to fulfill the Octet Rule
Ionic bond involves an attraction between ions of opposite charge
Covalent Bonds
electrons are SHARED, STRONGEST chemical bond
Allows for satisfying the Octet Rule AND charge differentials
Name for type of covalent bond involves PAIRS of shared electrons
Cations and Anions included under Ionic and Covalent bonds
Cations: loss of electron
Anions: gain of electron
Remember rule of who gains and who loses
Nonpolar vs Polar
nonpolar: electrons SHARED EQUALLY; strongest bond
polar: electrons SHARED UNEQUALLY
Non polar vs polar effects how thing react/work as well
Non polar fold one way(partial charge)
Polar folds equally both ways(partial charge)
NON POLAR MOLECULES DO NOT DISSOLVE IN WATER
Hydrogen in Bonds and interaction with water
Hydrogen bonds = weak (But because so many (trillions in single water droplets, can overwhelm other bonds))
Solvent: dissolves other things
Solutes are dissolved into the solvent(water in this case)
Hydrophobic: water fearing(lots of non polar, covalent bonds)
Hydrophillic: water loving(polar or ionic bonds, a charge)
oIMAGE SLIDE OF NACL Showing how charges of it react with water/hydrogen bonds in water
Hydrogen ions = hydroxide ions
Adhesion
water molecules that adhere to the glass, pull upward at the perimeter
Cohesion
ability of water molecules to stick to themselves
Example: spider non polar bond/lipids allow it to sit on top of the water without breaking through; Can change with heat
Water molecules at the surface from hydrogen bonds with nearby water molecules and reist the upward pull of adhesion
Buffers
Buffers prevent large shifts in pH
Example: if pH of 2 given a strong base to increase pH to 10, it will increase rapidly
If solution is a buffer, will prevent rapid change until out of buffer range
Point of buffer is to keep body cells at functioning state if not an exact amount
Most biological buffers consist of a pair of molecules, one an acid and one a base
If blood gets too acidic, can create carbonic acid to bring to normal levels
Important elements of Periodic Table for Life
90 naturally occuring elements, 12 important for human life
96.3% is CHON(carbon, hydrogen, oxygen, and nitrogen)
12: Carbon, Oxygen, Hydrogen, Nitrogen, Sodium, Chlorine, Calcium, Phosphorous, Potassium, sulfur, Iron, Magnesium
Sodium to sulfur considered electrolytes; Deals with protein; Iron vary small amount, but NEEDED top move cells around body
Identify noble gases and what is special about their valence shell
Noble gases: full valence shell, not really reactive because of this
Helium, Neon, Argon, Krypton, Xenon, Radon, and Oganesson
Octet Rule: a full 8 electrons, each atom must balance its need to fill the outermost shell with a need to balance charges
Which elements ionize and participate in ionic bonds?
Ionic: atoms EXCHANGE electrons in order to fulfill the Octet Rule
Ionic bond involves an attraction between ions of opposite charge
Solve charge imbalance by associating with each other
Occur between a metal and a nonmental
How many valence electrons are given up/taken on?
It is based on the placement in the periodic table; varies in ways to be a full “noble” shell
Which elements form covalent bonds, and how many can they form?
Covalent: electrons are SHARED, STRONGEST chemical bond; Allows for satisfying the Octet Rule AND charge differentials
Name for type of covalent bond involves PAIRS of shared electrons; Occur between two NON METALS; Can have single, double, and triple covalent bonds
Electrons without full valence shell do not like it so two hydrogen will bond with each other
Valence Concepts
Valence electrons; Electrons in the outermost shell of the atom, called the “valence shell”; Can form chemical bonds when outermost shell is not full
Valence of an atom: number of unpaired valence electrons; Full valence shell = chemically unreactive
Different atoms have different numbers of unpaired electrons
Example: NaCL
Na has loss of electron to have cation formation(positive charge), Cl has gain of electron to have anion formation(negative charge)
Identify acidic vs basic substances on the pH scale
pH scale slide, logarithmic scale, looking at exponent to identify
excess of OH = basic(lye, household bleach, household ammonia, milk of magnesia, baking soda, seawater)
excess of protons = acidic( black coffee, tomatoes, wine, vinegar, soft drinks, lemon juice, stomach acid)
water = neutral, 10^-7, 7
**NOTE: chemists do lots of rounding, biologists do not(Example: blood considered basic to biologists, considered neutral to chemists; Actual range would equal death, so different for biology)
Measures the concentration of free protons (H+) relative to hydroxyl ions (OH); Solutions that consume H+ are basic, those that generate H+ are acidic
VIEW CONTINUM ELECTRON SHARING
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