atom basic unit of matter. subatomic particles protons - neutrons - electrons - positively charged...
TRANSCRIPT
Subatomic particles• Protons - • Neutrons - • Electrons -
Positively charged (+)
Not charged (neutral)
Negatively charged (-)
Bind together to form the nucleus
Electrons Protons
Neutrons
Nucleus
Nonradioactive carbon-12 Nonradioactive carbon-13 Radioactive carbon-14
6 electrons6 protons6 neutrons
6 electrons6 protons8 neutrons
6 electrons6 protons7 neutrons
6
CCarbon12.011 Mass number
The Sum of protons and neutrons in the nucleus of an atom is its mass number
Radioactive isotopes• Can be dangerous
• Can be used practically–Radioactive dating
–Treat cancer
–Kill bacteria
Compounds• A substance formed by the
chemical combination of two or more elements in definite proportions
• Ex) H2O, NaCl
Sodium atom (Na) Chlorine atom (Cl) Sodium ion (Na+) Chloride ion (Cl-)
Transferof electron
Protons +11Electrons -11Charge 0
Protons +17Electrons -17Charge 0
Protons +11Electrons -10Charge +1
Protons +17Electrons -18Charge -1
• If an atom loses an electron it becomes positive
• Ex: All metals
• If an atom gains an electron it becomes negative
• Ex:All nonmetals
Molecule• The structure that results when
atoms are joined together by a covalent bond
• Both elements are nonmetals
• Smallest unit of most compounds
Van der Waals Forces• A slight attraction that
develops between the oppositely charged regions of nearby molecules due to unequal sharing of electrons
1. Describe the structure of an atom.
Atoms are made up of protons and neutrons in a nucleus. Electrons are in constant motion in the space around the nucleus.
2. Why do all isotopes of an element have the same chemical properties
They have the same number of electrons
3. What is a covalent bond?
A bond formed when electrons are shared between atoms
4. What is a compound? How are they related to molecules
A compound is a substance formed by the chemical combination of two or more elements in definite proportions. A molecule is the smallest unit of most compounds
5. How do Van der Waals forces hold molecules together?
When the sharing of electrons are unequal, a molecule has regions that are charged. An attraction can occur between oppositely charged regions of nearby molecules
6. How are ionic bonds and Van der Waals forces similar? How are they different?
In both cases, particles are held together by attractions between opposite charges. The difference is that ionic charges are stronger
• The solid lines between the O and the H
represent covalent bonds• In covalent bonds, electrons between
the atoms are shared.
• In some kinds of molecules, the electrons
• are shared equally between two atoms.
6. We say that those are nonpolar covalent bonds.
• In water, though, oxygen and hydrogen
do NOT share their electrons equally with each other so we say that there is a polar covalent bond between them.
• Because the oxygen atom is pulling negative charges toward itself, this makes oxygen take on a partial negative charge.
• 9. The hydrogen atom is having negative
• electrons pulled away from it, so the • 2 hydrogen atoms will take on a partial• positive charge.
• When another water molecule comes in, the partial negative oxygen of one water molecule will hydrogen bond with the partial positive hydrogen of another water molecule.
• 11. Hydrogen bonds are very weak, but • they are very important in molecules like DNA and
proteins.
• Hydrogen bonds are also responsible for the many properties of water, such as: A. Cohesion:
the attraction of molecules of the same kind (water molecules to other water molecules)
B. Adhesion: the attraction among molecules of different substances
(water molecule to something else)
The Big Idea
• Much of our planet is covered in water
• Water is necessary for life to exist• If life exists on other planets, there
most likely is water present• Water has many properties that
make life possible
Hydrogen Bonds• Because of waters partial charges,
they can attract each other and create hydrogen bonds
• Not as strong as covalent or ionic bonds
• Waters ability to create multiple hydrogen bonds gives it many special properties
Mixture• Material composed of two or more
elements or compounds that are physically mixed but not chemically combined
• Ex.) salt & pepper, earths atmosphere
Solutions• Mixture of two or more
substances in which the molecules are evenly distributed
• Ex.) salt water
• Settles out over time
Suspensions• Mixture of water and non-
dissolved materials
• Separate into pieces so small, they never settle out
• Ex: water and oil
Types of solutions• A dilute solution is weak solution• A concentrated solution is strong.• An unsaturated solution contains less
dissolved solute than it can hold at a given temp.
• A saturated solution contains all of the solute it can hold at a given temp.
• A Super saturated solution containing more solute than it can normally hold at a given temp.
( Crystals are often seen in this type of solution).
What is the pH scale?
• measure of the concentration of hydrogen ions in a solution
• Always shows reading between 0-14• pH between 0-7 is an acid• pH between 7-14 is a base• pH 7 is neutral. • neutral: neither acidic nor basic
*Tastes sour*Conducts electricity
*Corrosive to skin*Can eat through metal
*Formulas starts with “H”*Always releases hydrogen ions (H+)
when dissolved in water*pH is between 0-7
What is an acid?
*Tastes Bitter*Conducts electricity
*Corrosive to skin*Feel slippery
*Formulas ends with “OH”*Always releases hydroxide ions (OH¯) when dissolved in water
*Red litmus paper into Blue (indicator)
*pH between 7-14
What is a base?
What is an electrolyte?
• electrolyte : substance that conducts an electric current when it is dissolved in water
• ionization : formation of ions
• Nonelectrolyte: substance that will not conduct an electric current when it is dissolved in water .
Buffers• Weak acids or bases that can
react with strong acids or bases to prevent sharp, sudden pH changes
1. Use the structure of a water molecule to explain why its polar
Oxygen atom has greater attraction for electrons, therefore the oxygen atom is negative and the hydrogen end is positive
2. Compare acidic and basic solutions in terms of their H+ ion and OH- ion concentrations
Acid have more H+ ions than OH-
ions, and bases have more OH-
ions than H+ ions
3. What is the difference between a solution and a suspension?
In a solution, all components are evenly distributed. In a suspension, un-dissolved particles are suspended
4. What does pH measure?
The concentration of H+ ions in a solution
5. The strong acid hydrogen floride (HF) can be dissolved in pure water. Will the pH of the solution be greater or less than 7?
less than 7
• Most of the compounds that make up living things contain carbon. In fact, carbon makes up the basic structure, or “backbone,” of these compounds. Each atom of carbon has four electrons in its outer energy level, which makes it possible for each carbon atom to form four bonds with other atoms.
• As a result, carbon atoms can form long chains. A huge number of different carbon compounds exist. Each compound has a different structure. For example, carbon chains can be straight or branching. Also, other kinds of atoms can be attached to the carbon chain.
Section 2-3
Interest Grabber
Life’s backbone
Carbohydrates• Compounds made up of carbon,
hydrogen, and oxygen atoms usually in a ratio of 1:2:1
• Main source of energy
• The monomers of starch are sugars
• Single sugar molecules are called monosaccharides
• The large macromolecules formed from monosaccharides are known as polysaccharides
Proteins• Macromolecules that contain
nitrogen as well as carbon, hydrogen, and oxygen
• Proteins are polymers of molecules called amino acids
• More than 20 different amino acids, can join to any other amino acid
• The instructions for arranging amino acids into many different proteins are stored in DNA
• Each protein has a specific role• The shape of proteins can be very
important
Nucleic Acids• Macromolecules containing hydrogen,
oxygen, nitrogen, carbon, and phosphorus
Double Helix
Nucleotides• Consists of 3 parts: 5-carbon sugar,
phosphate group and nitrogen base
Nitrogen Base
5-Carbon Sugar
Phosphate group
2 kinds of nucleic acids• RNA (ribonucleic acids) –
contains sugar ribose
• DNA (deoxyribonucleic acid) – contains sugar deoxyribose
1. Name four groups of organic compounds found in living thingscarbohydrate, lipid, protein, nucleic acids
2. Describe at least one function of each group of organic compoundscarbohydrates – energylipids – store energyproteins – form tissuenucleic acids – transmit hereditary information