Ch. 2 Chemistry

Question 1

what is an element?

Answer 1

a substance that cannot be broken down to other substances through chemical reactions - ex, sodium, chlorine, oxygen

Question 2

what is a molecule?

Answer 2

a group of two or more atoms [elements] that form the smallest functional unit of a compound

Question 3

what is a compound?

Answer 3

a substance containing two or more different elements combined in a fixed ratio: NaCl, H20, Co2

Question 4

what is an isotope?

Answer 4

different FORMS of atoms of ONE ELEMENT: ex carbon 12 has 6 neutrons, carbon 13 has 7, carbon 14 has 8

Question 5

what is an ion?

Answer 5

a bond formed when one atom takes an electron from another atom

Question 6

what is an atom?

Answer 6

the smallest part of an element, composed of + protons, - electrons, and neutrons

Question 7

what is atomic number?

Answer 7

the “name” of an element, based on the # of protons it has. ex: hydrogen has 1 proton, so it has an atomic # of 1

Question 8

what is mass number?

Answer 8

the # of neutrons in an atom + the # of protons

Question 9

what is a valence shell?

Answer 9

the outermost shell of an atom, where electrons are that can be taken / shared between atoms

Question 10

what is an electron?

Answer 10

a negatively charged subatomic particle, responsible for giving charge to atoms

Question 11

what elements make up the bulk of living organisms?

Answer 11

C , H , O , N , P , S

Question 12

what is a chemical bond?

Answer 12

an interaction between atoms that holds them together. atoms try to join together in combinations that fill their valence shells

Question 13

what is a covalent bond?

Answer 13

a bond where atoms equally share electrons

Question 14

what is a molecular bond?

Answer 14

two or more atoms held together by covalent bonds

Question 15

what is a single bond?

Answer 15

the sharing of one PAIR of valence electrons (2)

Question 16

what is a double bond?

Answer 16

the sharing of two PAIRS of valence electrons (4)

Question 17

what are valence eletrons?

Answer 17

-electrons in the valence shell of an atom
-determines the reactivity of the element

Question 18

what is electronegativity?

Answer 18

the attraction of an atom for the electrons in a covalent bond: the more electronegative an atom, the stronger it pulls shared electrons towards itself

also dictates the type of bond shared by atoms

Question 19

what is a nonpolar covalent bond?

Answer 19

a covalent bond where atoms have similar electronegativities = equal sharing

Question 20

what is a polar covalent bond?

Answer 20

a covalent bond where atoms have unequal electronegativities = unequal sharing, creates partial charges on atoms

Question 21

what is an ionic bond?

Answer 21

a chemical bond between two IONS. creates IONIC COMPOUNDS, or SALTS

Question 22

what is a hydrogen bond?

Answer 22

a bond formed when a hydrogen atom covalently bonded to one electronegative atom is attracted to another electronegative atom in a different molecule

Question 23

what are van der waals interactions?

Answer 23

interactions where transiently positive and negative regions of molecules attract each other

Question 24

what are hydrophobic interactions?

Answer 24

-when certain macromolecules have hydrophobic portions, they get pushed away by water & do not mix/interact

-ex - cell membranes, oil and water

Question 25

what is chemical equillibrium?

Answer 25

when the RATES of forward and reverse reactions are equal. the AMOUNT of product vs reactant may not be equal, but their rate of reaction is

Question 26

what is a chemical reaction?

Answer 26

the rearranging of atoms between molecules and ions: substrates / reactants are converted into products