Basic Chemistry

The Nature of Matter Matter refers to anything that takes up space and has mass. Matter refers to anything that takes up space and has mass. Matter is composed of elements, substances that cannot be broken down into another substance. Matter is composed of elements, substances that cannot be broken down into another substance. There are 92 natural elements. There are 92 natural elements. Living organisms are made primarily of six elements. Living organisms are made primarily of six elements.

The Nature of Matter

Elements: Made up of tiny particles called atoms Made up of tiny particles called atoms Each has its own Each has its own name name atomic number atomic number atomic symbol atomic symbol Name Number Symbol Hydrogen 1 H Aluminum 13 Al Sodium 11 Na

Atomic Structure Atomic Structure Atoms have three main sub atomic structures : Name Charge Mass Location Proton + 1 amu inside nucleus Electron - 1/1837 amu around nucleus Neutron o 1 amu inside nucleus

Atomic Structure All atoms of the same element have the same number of protons It is also equal to the atomic number

The Periodic Table The elements are organized to form the periodic table. The elements are organized to form the periodic table. The columns in the table are groups. The columns in the table are groups. The rows in the table are periods. The rows in the table are periods. Elements in groups have similar chemical and physical characteristics. Elements in groups have similar chemical and physical characteristics.

The Periodic Table

Atomic Structure The Atomic Mass is the number of protons and neutrons Na Mass Atomic Number Number of protons: 11 Number of neutrons: 12 (23 – 11) Number of electrons 11

Composition of Matter- Elements Symbols to know: Symbols to know: C Carbon Na Sodium Mg Magnesium O Oxygen P Phosphorus Fe Iron H Hydrogen S SulfurCa Calcium N Nitrogen Cl Chlorine K Potassium

Composition of Matter- Elements Isotopes Many elements have isotopes. Isotopes have the same atomic number but a different atomic mass (they have more or less neutrons)

Composition of Matter- Elements Isotopes are represented differently, showing their atomic mass. Examples: carbon – 14 is an isotope of carbon with a mass of 14 (the normal mass is 12) iodine – 131 is an isotope of iodine with a mass of 131 (the normal mass is 127)

Composition of Matter- Elements Certain isotopes are very unstable and release energy as they “fall apart” or disintegrate. These isotopes are called radioactive isotopes or radioisotopes. This radiation can be detected with a Geiger counter.

Uses of Radioactive Isotopes Radioactive isotopes can be used as tracers to follow the movement of that element. Radioactive isotopes can be used as tracers to follow the movement of that element. Radioactive isotopes can be used to sterilize medical and dental instruments. Radioactive isotopes can be used to sterilize medical and dental instruments. Radioactive isotopes can also be used to kill cancer cells. Radioactive isotopes can also be used to kill cancer cells.

Uses of Radioactive Isotopes

Atomic Structure Electrons are found in energy levels outside the nucleus Electrons are found in energy levels outside the nucleus The first energy level holds two electrons The first energy level holds two electrons The second energy level holds eight electrons The second energy level holds eight electrons The third energy level holds eight electrons The third energy level holds eight electrons Other levels can hold more Other levels can hold more Octet Rule: Stable atoms have eight electrons in their outer level Octet Rule: Stable atoms have eight electrons in their outer level

Atomic Structure Electrons in the outermost shell are called valence electrons Electrons in the outermost shell are called valence electrons All elements in the same column (group) of the Periodic table have the same number of valence electrons All elements in the same column (group) of the Periodic table have the same number of valence electrons The valence electrons determine how an element will react The valence electrons determine how an element will react

Arrangements of Electrons in an Atom

Chemical Bonds A group of atoms bonded to one another form a molecule. A group of atoms bonded to one another form a molecule. If the molecule has more than one type of element present it is a compound. If the molecule has more than one type of element present it is a compound. Different types of bonds hold molecules and compounds together. Different types of bonds hold molecules and compounds together.

Chemical Formulas Types of Formulas Molecular formulas show the actual composition of a compound using symbols of elements and their proportions Examples: Water Methane Carbon dioxide H 2 O CH 4 CO 2 H 2 O CH 4 CO 2

Chemical Formulas Structural formulas are formulas that show the bonding of elements in a compound and their relative positions Examples: Water Methane Carbon dioxide H H O H H O H C H H C H H O H C O

Composition of Matter - Compounds Chemical Bonds A chemical bond is the “glue” that holds the elements together in compounds. The valence electrons determine how an element will react and bond

Types of Chemical Bonds Charged atoms, or ions, can form when atoms lose or gain electrons. Charged atoms, or ions, can form when atoms lose or gain electrons. Atoms that lose an electron become Positive Atoms that lose an electron become Positive Atoms that gain electrons become Negative Atoms that gain electrons become Negative Positive and negative ions are attracted to one another and bond together in ionic bonds. Positive and negative ions are attracted to one another and bond together in ionic bonds. Usually between a metal and non metal that are far apart horizontally on the periodic table. Usually between a metal and non metal that are far apart horizontally on the periodic table. A salt is a dry solid composed of atoms connected by ionic bonds. A salt is a dry solid composed of atoms connected by ionic bonds.

Types of Chemical Bonds Ionic Bonds Sodium (one valence electron) Loses the electron Becomes positive (+) Chlorine (seven valence electrons) Gains the electron Becomes negative (-) Opposites Attract! Each outer shell has eight electrons

Types of Bonds formed when electrons are shared among elements in a compound. formed when electrons are shared among elements in a compound. usually formed between two non metals or a non metal and hydrogen usually formed between two non metals or a non metal and hydrogen Models or diagrams can be drawn to show the shared electrons Models or diagrams can be drawn to show the shared electrons Covalent bonds

Types of Chemical Bonds

Chemical Equations Equations show the: chemicals that are reacting chemicals that are reacting products that are made products that are made amount of each chemical involved amount of each chemical involved In equations, reactants are on the left the products are on the right. Example: Water produces hydrogen and oxygen 2H 2 O 2H 2 + O 2

Chemical Reactions Molecules that participate in a reaction are reactants. Molecules that participate in a reaction are reactants. Molecules formed by a reaction are products. Molecules formed by a reaction are products. 6 CO H 2 O  C 6 H 12 O O 2 carbon dioxide wateroxygenglucose The chemical reaction for photosynthesis

Water, Acids, Bases and pH Dissociation occurs when an ionic compound separates into its ions. Example: Salt (NaCl) breaks apart into Na+ and Cl- Na + Cl -

Acids and Bases When water dissociates, it releases an equal number of ions. When water dissociates, it releases an equal number of ions. Hydrogen ions (H + ) Hydrogen ions (H + ) Hydroxide ions (OH - ) Hydroxide ions (OH - ) H – O – H H + + OH -

Water, Acids, Bases and pH Acids Acids will dissociate in water to release a hydrogen ion (H+) Examples: HClH 2 SO 4 HC 3 H 5 O 3 (Notice the H at the front of the formula)

Water, Acids, Bases and pH Bases will dissociate in water and release OH- (hydroxyl) ions They have a low concentration of H+ Examples: NaOH KOH (notice they end in –OH)

pH and the pH scale The pH is a mathematical way of indicating the number of H + ions in a solution. The pH is a mathematical way of indicating the number of H + ions in a solution. The lower the number, the higher the concentration. The lower the number, the higher the concentration. The pH scale is used to express acidity or basicity (alkalinity). The pH scale is used to express acidity or basicity (alkalinity).

Water, Acids, Bases and pH Acids have a low pH (less than 7) and bases have a high pH (more than 7) Strong Neutral Strong Strong Neutral Strong Acid Base Acid Base The farther away from neutral, the stronger the acid or base.

Water, Acids, Bases and pH Extremely acidic: lemon=2.5; vinegar=3.0; stomach acid=2.0 Extremely acidic: lemon=2.5; vinegar=3.0; stomach acid=2.0 Very strongly acid: tomatoes=4.5 Very strongly acid: tomatoes=4.5 Strongly acid: carrots=5.0; asparagus=5.5; cabbage=5.3 Strongly acid: carrots=5.0; asparagus=5.5; cabbage=5.3 Moderately acid: potatoes=5.6 Moderately acid: potatoes=5.6 Slightly acid: salmon=6.2; cow's milk=6.5 Slightly acid: salmon=6.2; cow's milk=6.5 Neutral: saliva=6.6–7.3; blood=7.3; shrimp=7.0 Neutral: saliva=6.6–7.3; blood=7.3; shrimp=7.0 Slightly alkaline: eggs=7.6–7.8 Slightly alkaline: eggs=7.6–7.8 Moderately alkaline: sea water=8.2; sodium bicarbonate=8.4 Moderately alkaline: sea water=8.2; sodium bicarbonate=8.4 Strongly alkaline: borax=9.0 Strongly alkaline: borax=9.0 Very strongly alkaline: milk of magnesia=10.5, ammonia=11.1; Very strongly alkaline: milk of magnesia=10.5, ammonia=11.1;

Water, Acids, Bases and pH Mixing an acid with a base a chemical reaction will change the pH of the mixture Mixing an acid with a base a chemical reaction will change the pH of the mixture Hydrogen ions will react with the hydroxyl ions and form water Hydrogen ions will react with the hydroxyl ions and form water H + + OH - HOH If the ions are in equal amounts, the mixture becomes neutral (pH 7) If the ions are in equal amounts, the mixture becomes neutral (pH 7) This is called a neutralization reaction. This is called a neutralization reaction. The remaining ions form a salt. The remaining ions form a salt.

Buffers and pH Within the body, the pH is kept in a narrow range to maintain health. Within the body, the pH is kept in a narrow range to maintain health. A buffer is a chemical or combination of chemicals that keeps a pH within a given range. A buffer is a chemical or combination of chemicals that keeps a pH within a given range. Buffers resist changes in pH by taking up extra H + or OH - from solution. Buffers resist changes in pH by taking up extra H + or OH - from solution.

Buffers and pH