BIOL Ch 2

atom

fundamental structural units of matter and composed of protons, neutrons, and electrons

protons

positively charged particles in the nucleus

neutrons

neutrally charged particles in the nucleus

electrons

negatively charged particles orbiting around the nucleus

why are atoms neutral?

they have the same number of protons and electrons

atomic number

the number of protons in the nucleus of an atom, defining value of an element (\# p)

atomic mass

the total mass of an element's protons and neutrons (p + n)

element

a substance that cannot be broken down by ordinary chemical reactions

atoms belong to one of ... types of naturally occurring elements

92

isotopes

atoms of the same element that have different numbers of neutrons

radioactive isotopes

isotopes that spontaneously break apart, forming different atoms and releasing energy

at room temperature, elements may occur as ...

solids, liquids, or gases

electron shells

location where electrons are distributed around the nucleus

energy level

the first electron shell, holds 2 electrons

how many electrons can the second electron shell hold?

8

nucleus provides ...

stability

chemical bonds

the force of attraction between atoms that hold them together, there are many different types

electrons interact with ...

other atoms

energy capture and release

1. electron shells correspond to energy levels
2. when energy excited an atom, the electrons jump from a lower to a higher energy shell
3. the electron falls back into its original shell --releasing energy

molecules

two or more atoms, from the same of different elements

compound

a substance made of atoms of different elements

reactions between atoms depend upon the configuration of electrons in ..

the outermost shell

inert atoms

atoms that will not react with other atoms when its outermost electron shell is stable

reactive atoms

atoms that react with other atoms when its outermost electron shell is only partially full with electrons

how do reactive atoms gain stability?

through electron interactions (chemical reactions)

how to empty the outermost shell of an atom

electrons can be lost

how to fill the outermost shell of an atom

electrons can be gained

when can electrons be shared with another atom?

when both atoms have full outermost shells

hydrogen and oxygen

two atoms that gain stability by interacting with one another

single electrons from each of the two ... atoms fill the outer shell of an ... atom

hydrogen, oxygen

free radical

a molecule in which atoms have one or more unpaired electrons in their outer shells

why are free radicals dangerous?

highly unstable and reactive, steal electrons (destroying their molecules), attacks can cause cell death, implicated in heart disease, Alzheimer's, cancer, and aging

what can render free radicals harmless?

antioxidants (e.g., vitamins C and E)

chemical reaction

process by which new chemical bonds are formed or existing bonds are broken, converting one substance into another

major types of chemical bonds

ionic, covalent, hydrogen

ionic bond

an electron is transferred, creating positive and negative ions that attract one another

covalent bond

electrons are shared, two types nonpolar and polar

nonpolar covalent bond

a covalent bond in which the atoms exert the same fulling force and the electrons are shared equally by the two atoms

polar covalent bond

a covalent bond in which electrons are not shared equally

ions

atoms that have lost or gained electrons

oxidation

atoms that have lost electrons and become positively charged ions (Na+)

reduction

atoms that have gained electrons and become negatively charged ions (Cl-)

ionic bonds

oppositely charged ions that are attracted to each other and are bound into a molecule

salt crystals

formed by a repeated, orderly arrangement of sodium and chloride ions

covalent bonds

a bond created when an atom with a partially full outermost electron shell becomes stable by sharing electrons with another atom

covalent bonds are found in ...

H2 (H-H, single bond)

O2 (O=O, double bond)

N2 (N≡N, triple bond)

H2O

what types of bonds are stronger than the other?

covalent are stronger than ionic

atoms with a greater positive nuclear charge pull more strongly on ...

electrons in a covalent bond

hydrogen bond

attractive forces between polar molecules, form when partial opposite charges in different molecule attract each other, comparatively weak but can be strong

hydrogen bonds can only occur between hydrogen and ...

oxygen, nitrogen, or fluorine

cohesion

the tendency of molecules of a substance to stick together

hydrogen bonding between water molecules produces what kind of cohesion

high

surface tension

cohesion of water molecules along a surface

solvent

a liquid substance capable of dissolving other substances (E.g., water)

solution

a homogeneous mixture of two or more substances

hydrophilic

water-soluble molecules

hydrophobic

water-insoluble molecules that repel and drive together uncharged and nonpolar molecules

hydrophobic interaction

the tendency for hydrophobic molecules to cluster together when immersed in water

water-based solutions can be ...

acidic, basic, or neutral

ionized

when molecules break apart into ions

acidic solutions

when [H+] \> [OH-] (E.g., lemon juice and vinegar)

basic solutions

when [OH-] \> [H+] (E.g., baking soda, chlorine bleach, and ammonia)

pH scale

measurement used to determine degree of acidity of a solution

pH of 0-6.999 is ...

acidic

pH of 7 is ...

neutral

pH of 7.001-14 is ...

basic

buffer

a compound that accepts or releases H+ in response to a pH change, helps to maintain a relatively constant pH in a solution

pH of blood

~7.4 (slightly basic)

what happened if blood becomes too acidic?

bicarbonate accepts and absorbs H+ to make carbonic acid

what happens if blood becomes too basic?

carbonic acid liberates hydrogen ions to combine with OH- to form water

effects of temperature change on enzymes

low or high can damage them and slow down important chemical reactions

specific heat

the energy required to heat 1 gram of a substance by 1°C

temperature reflects ...

the speed of molecular motion

energy required to heat water

one calorie to raise 1g by 1°C

heat of vaporization

the amount of heat needed to cause a substance such as water to evaporate, it uses the heat from its surroundings and cools the nearby environment (sweating)

ice as an unusual solid

less dense than liquid form and floats, molecules spread during freezing process

process of freezing in bodies of water

top to bottom, never freeze completely to the bottom (wildlife is safe!)