Biology Chapter 2 Flashcards
Atomic theory
The concept of an atom
Born in Ancient Greece (~500bc)
Chemical basis of life
Atoms, molecules, and properties of H2O
Atomic structure
The nature of an atom
Proton, neutron, electron, ion, isotopes
Atomos
All matter is made up of tiny invisible particles named
Matter
Has mass and occupies space
Matter is
Composed of chemical elements.
Gas, solid, liquid, plasma
Element
Has atomic characteristics and cannot be broken down into other substances
Atom
Smallest unit of matter with retains the chemical and physical properties of an element
Proton
Electron
Neutron
Positive
Negative
No charge
Atomic structure
Nucleus composed of protons and neutrons and surrounded by orbiting electrons. Protons and neutrons have roughly the same mass (1 dalton)
Atomic number
Same as number of protons
Atomic mass and weight
Mass of protons and neutrons combined
All atoms of an element have?
The same atomic number and mass
In a neutral atom?
Number of protons = number of electrons
Isotopes
Atoms must have a certain # of protons to retain the characteristics of a given element, but # of neutrons sometimes vary.
Unstable and decay at constant rate
Electrons
Orbit around nucleus (drawn by protons + charge)
Valence # in valence dictates what?
Outermost shell
The reactivity of the atom
Atoms will?
Accept, donate, or share electrons with other atoms to fill the valence shell and become stable.
Chemical bonds
Attractive forces between atoms that result from accepting, donating, or sharing electrons.
Bonding capacity?
of bonds atom will form
Octet rule
Valence she’ll is full when it contains 8 electrons ( most stable)
Molecule
2 or more atoms held together by chemical bonds (NaCL, H2)
Compound
Substance composed of 2 or more different atoms (NaCL)
Ions
Atoms in which the number of electrons doesn’t equal that of protons
Cation
Atom which loses electron is now positively charged
Anion
Atom which gains electron is now negatively charged
Types of chemical bonds
Ionic bonds Covalent bonds Polar covalent bonds Hydrogen bonds Non polar covalent bonds
Ionic bonds
Complete transfer of electrons
Atoms held together by electrostatic attraction between oppositely charged cation and anion
Ionic bonding
Resulting in compound neutral
Bonds are weak
Covalent bonds
Chemical bond formed Between 2 atoms by the sharing of electrons
Strength of bond increases with the # of shared electrons
Polar covalent bonds
One atom of a molecule attracts electron more strongly than other atom (unequal sharing)
Hydrogen bond
Occurs when + hydrogen atom of 1 polar molecule is attracted to the - atom of another polar molecule
Occurs in DNA and protein
Water
75% earth made up of
Vertebrates composed up to 66% water
Unique properties of water
Polar molecule
Molecules bound to each other by hydrogen bonds
Why water is unique
Extremely high specific heat
Ice formation
Cohesion
High polarity
Ice formation
H+ bonds in water form a crystal lattice which traps air
Causes solid water to be less dense than liquid (ice)
Cohesion
Attraction of water molecules to each other. Surface tension caused by cohesion
Adhesion
Attraction of water molecules to polar molecules
High polarity
Polar hydrophilic (water loving) molecules are highly soluble in water Non polar hydrophobic molecules are soluble in water (oils)
pH
Is the potential hydrogen of a substance
pH of pure water is 1 dalton or 1 H+ per liter of water
pH scale on 0-14
pH 0-6.9 is acidic
Readily dissociate in water and donate H+ ions
Adding H+ ions decreases pH
Buffers
Accept or donate H+ ions
Carbonic acid buffers the pH of the blood
