ap chapter 2 closed notes
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Chapter 2 Notes
The Chemical Context of Life
Concept 2.1Organisms are composed of __________:
anything that takes up space or has mass
___________: a substance that cannot be broken down by chemical reactions
___________: substance consisting of two or more elements in a fixed ratio
Concept 2.1Life requires about 25 elements4 of those make up 96% of living matter
_______________________________________________________
Trace Elements are those that are required in only minute quantities-ex. Iron, iodine
Concept 2.1
Concept 2.2_________: smallest unit of matter that
still retains the properties of an element
___________________: Protons (+), Neutrons (0), Electrons (-)
Protons and Neutrons have a mass of 1 dalton. Electrons have no mass
Concept 2.2___________________: # of protons_______________: sum of protons +
neutrons__________________: different atomic
forms of an element.-ex. Carbon-12 (99%), Carbon-13 (1%), Carbon-14 (<1%)
Concept 2.2C-12 and C-13 are stable. C-14 is
unstable, and radioactive. It will decay giving off particles and energy.
Carbon-14 will decay into Nitrogen
Concept 2.2An atom’s electrons vary in the
amount of energy they possess. ____________: the ability to do work._______________: energy that matter
stores because of its position or location
Electrons have potential energy because of their position in relation to the nucleus.
(a) A ball bouncing down a flight of stairs provides an analogy for energy levels of electrons
Third shell (highest energylevel)
Second shell (higherenergy level)
Energyabsorbed
First shell (lowest energylevel)
Atomicnucleus
Energylost
Concept 2.2
Concept 2.2The different states of potential energy
that electrons have in an atom are called energy levels or electron shells.- the first shell has the lowest energy. The second shell has more than the first, etc.
__________________: those in the outermost shell
Concept 2.2Hydrogen
1H
Lithium3Li
Beryllium4Be
Boron5B
Carbon6C
Nitrogen7N
Oxygen8O
Fluorine9F
Neon10Ne
Helium2He
Atomic number
Element symbolElectron-distributiondiagram
Atomic mass
2He
4.00Firstshell
Secondshell
Thirdshell
Sodium11Na
Magnesium12Mg
Aluminum13Al
Silicon14Si
Phosphorus15P
Sulfur16S
Chlorine17Cl
Argon18Ar
Atoms will bond with others to gain stability
________________: sharing of a pair of valence e- by two atoms-ex. Hydrogen atoms will share their electrons. They become H-H
Concept 2.3
Concept 2.3
Concept 2.3__________________: the attraction of
an atom for the electrons of a covalent bond
____________________: when the electrons are shared equally
____________: when one atom is bonded to a more electronegative atom
Concept 2.3 –
+ +
H H
O
H2O
Atoms and Molecules_____________: when two atoms are so
unequal in their attraction for electrons that one atom will strip the electrons from its partner
_________: a charged atom; cation has a positive charge, anion has a negative charge (ca+ion; a negative ion)
Compounds formed by ionic bonds are salts
Concept 2.3
Na Cl Na Cl
NaSodium atom Chlorine atom
Cl Na+
Sodium ion(a cation)
Cl–Chloride ion
(an anion)
Sodium chloride (NaCl)
The advantage of weak bonding is that the contact can be brief
_______________: H is covalently bonded to an electronegative atom and attracted to another electronegative atom.-ex. Water and ammonia
Atoms and Molecules
Concept 2.3 +
+
++
+
Water (H2O)
Ammonia (NH3)
Hydrogen bond
Atoms and Molecules________________: making and
breaking of chemical bonds.- starting material is reactants- ending material is products
__________________: point at which reactions offset one another.
Atoms and Molecules