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Atoms
The basic unit of _______________Nucleus: center of atom; contains protons
and _________________ Proton: positive charge Neutron: NO charge
Electron: _________charge Orbits the nucleus
_______________ Electrons:
Found in the outer most orbital
Are the electrons that form ___________ with other atoms
Atoms are neutral
Stable Atoms have a ___________ charge
Equal number of ________________ and electrons
+++++ equals - - - - -
The charges cancel each other out
Element________________: A pure substance that
consists entirely of one type of atom.Represented by one or two letter symbol
EX: C = Carbon Na = Sodium
Atomic ____________ = # protons in element # protons = # electrons
Atomic ___________ = protons plus neutrons
ISOTOPES: Atoms of the same element BUT have a different
number of neutrons.
For Ex: CARBON usually has 6 protons & 6 neutrons
• An Isotope of Carbon would have 6 protons & 7 neutrons
• The atomic # stays the same!!!! It is the same number as the number of protons
• So regular carbon & carbon’s isotope would have an atomic # of 6.
Isotopes
Nonradioactive carbon-12 Nonradioactive carbon-13 Radioactive carbon-14
6 electrons6 protons6 neutrons
6 electrons6 protons8 neutrons
6 electrons6 protons7 neutrons
________________ Elements
Have unstable nuclei that breaks down at a constant rate over time
Radiation given off can be dangerous, but useful in science and medicine.
Examples: Geologists using C14 to date rocks; cancer treatments, killing bacteria in food; tracers to follow through an organism
Compounds* formed by chemically combining ______ or
more elements
Examples: water (H20) – most abundance compound in living things and ________ ________(NaCl)
The physical and chemical properties of a compound are usually very different from the elements they were formed from
Chemical Bonds
1. Ionic Bonds
2. ___________________ Bonds (strongest bond)
3. Hydrogen Bonds
4. Van der Waals Forces (weakest bond)
Chemical Bonds Ionic Bonds: formed when 1 or more electrons are
____________________ from one atom to another – creating ions with opposite charges
___________: atom with a positive or negative charge
* due to the LOSS or GAIN of an
electron Na+ Cl-
Attraction between the charged ions form ionic bond
Creating Ions:
Positive ions have __________ an electron
Ex: Na+
Negative ions have __________ an electron
Ex: Cl-
Covalent BondsCovalent bond: formed when electrons are
__________________ between atoms
Strongest type of bond
Single bond→2 electron sharedDouble bond →______ electrons sharedTriple bond →6 electrons shared
__________________ Force
A slight attraction that develops between the oppositely charged regions of nearby molecules. A very _______________ bond
Van der Waals forces is what enables a gecko to climb up walls
Properties of Water H2OWater is neutralMolecule is bent at a 104.5° angle
___________________: uneven distribution of electrons between the O and H atoms
Hydrogen end of molecule has a positive charge. Oxygen end of molecule has a _______________
charge.
Hydrogen BondsHydrogen Bonds: bonds formed between
__________________ molecules. The negative end of one molecule is attracted to the positive end of another
H bonds hold water together
and
hold the inner parts of __________ together
Properties of Water cont.
Cohesion: attraction between molecules of the _________________ substance EX: water droplets = water molecules
sticking
together
Adhesion: attraction between molecules of _____________________ substances EX: water moving up a straw = water molecules
sticking to side of straw
Water properties continued:
Heat capacity is the capability of water to absorb heat without undergoing an increase in temperature. Water has a ________________ heat capacity.
Buoyancy – things less ________________ than water will float – when ice freezes, it is less dense than liquid water.
Properties of water continued:
Water __________________ things –
EX. 90% of blood plasma is water – blood transports oxygen & nutrients
• Things dissolve or ___________________ in water
EX. Nutrients dissolve in soil
• Water has a pH of 7 – it is neutral
Properties of water continued:
Surface Tension of Water - the surface of water sticks together by _________________ & allows it to behave as an elastic sheet.
Allows insects like the water strider to walk on water
pH Scale
pH scale: indicates the concentration of ________+ ions in a solution
pH Scale Ranges from 0 - 14
Acids
Acids: higher concentration of H+ ions than water
pH value below 7 (_______ - 6.9)
Strong acids pH 1 to 3
EX: lemon juice, stomach acid, polluted rainfall, vinegar
Bases
Bases: higher concentrations of _________ - ions than water
pH value above 7 (7.1 - _______)
Strong bases pH 11 to 14
EX: blood, milk, soap, bleach, sea water
____________________________:Cells can only tolerate small changes in
pHChemical Processes only work within a
specific pH rangeOrganism could die if subjected to major
pH changesOrganisms need to maintain
HomeostasisHomeostasis: process in which organisms
maintain a stable internal environment