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A neutron walks into a bar; he asks the bartender, 'How much for a beer?' The bartender looks at him, and says 'For you, no charge.' Two atoms bump into each other. One says 'I think I lost an electron!' The other asks, 'Are you sure?', to which the first replies, 'I'm positive.'
Atom: the smallest particle of an element. Everything is made of atoms Proton: positive particle in the nucleus Neutron: neutral particle in the nucleus Electron: tiny negative charge outside the nucleus Atoms are mostly…. … empty space! Element: a substance made of only one kind of atom, cannot be chemically or physically separated into other substances.
Atomic number: the number of protons in an atom. All elements are identified by their atomic number. For example, any element with 6 protons is Carbon, regardless of how many neutrons (or electrons) it has Atomic mass: the sum of the number of protons and neutrons.
Molecule: Two or more ATOMS bonded together. Examples: Water = H2O Oxygen = O2 Compound:Two or more different ELEMENTS bonded together.
Which of these is a molecule but not a compound? • Ar • NaCl • H2SO4 • H2
Homogenous mixture: substances are evenly distributed so that one part of the mixture can’t be distinguished from another. Example: stirring cream into your coffee heterogenous mixture: substances are not evenly distributed and can be distinguished from another. Example: soil, oil and vinegar
Ion: an atom or molecule that has a positive or negative electric charge because its number of protons is not equal to its number of electrons. Isotope: Atoms that have the same number of protons but different number of neutrons. They are the SAME element!
Atomic mass = protons + neutrons Atomic number = protons Writing the elements to show atomic mass and number This is “Carbon-14”. How many neutrons does it have? This is “Carbon-12”. How many neutrons does it have? Carbon-14 and Carbon-12 are different ????? of Carbon.
Chemical Formula: A description that uses numbers and symbols of elements to describe a molecule. H2O NaCl CaCl2 Periodic Table: A chart that lists the elements by atomic number and electron arrangement.
Use your periodic table! What’s the atomic number of Cobalt? What’s its atomic mass? How many protons does Calcium have? What element has 17 protons and 18 neutrons? What is its atomic number? What is its atomic mass?
Radioactive Elements Some elements are unstable, especially if they’re really massive, and spontaneously fall apart or decay. Why would nucleii tend to fall apart?? (Think about what protons do to each other) These unstable elements are called RADIOACTIVE. All elements with more than 83 protons are RADIOACTIVE.
Radioactive Elements They will continue to decay until they are stable (non-radioactive), even if it takes years. The amount of time it takes until half of the atoms in a radioactive sample have decayed is called its HALF-LIFE.
A radioactive sample has 1000 atoms. The graph shows the number of radioactive atoms remaining as a function of time. • What is the HALF-LIFE of this sample? • 50 years B) 80 years C) 150 years D) 400 years • B) 80 years Number of radioactive atoms Time in years
The individual columns are called GROUPS. Elements in the same GROUP react in similar ways!
Which elements will behave in similar ways? Ca Br O F Which are in the same GROUP?? Br and F
Metals Non metals How to remember?? In the alphabet…… “M” comes before “N”
Which of the following are metals: Calcium, Sulfur, Cobalt, Boron, Aluminum Metals: Calcium, Cobalt, Aluminum
e- Metals have “free electrons” (in their outer shell) that can move around- that’s how they conduct electricity Metals can DONATE those electrons Nonmetals will ACCEPT those electrons. Think of those electrons flowing like electricity flows from the metals over to the nonmetals
Don’t react with anything! Which element will accept electrons? Al S K Ne Well, Ne is the furthest to the right, but….. The last column is special- these are the inert or noble gases. They are completely unreactive, because their outer shell is full. So the right answer is….. Sulfur
The ability to accept electrons is called electronegativity. Which elements MOST readily accept electrons? The group of elements that only need ONE more electron to fill their outermost shell.
Which group needs only ONE more electron to fill its outer shell?? Group 17
Group 17 is called the Halogens. And, in this group, the element Fluorine has the highest “electronegativity” – the ability to accept electrons
Which element most readily accepts electrons? Zn N F As Nitrogen, Arsenic and Fluorine all will accept electrons, but Fluorine has the highest electronegativity!
Acids and Bases pH scale identifies acids and bases with a number: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Acids Neutral Bases How to remember??? In the alphabet, “A” is before “B”
Basic substances will turn litmus paper BLUE Acidicsubstances will turn litmus paper RED. Examples of acids: hydrochloric acid, lemon juice, vinegar Examples of bases: ammonia, soap, baking soda (often bases are slippery stuff!)
How do you know if it’s an acid or base? Acids have H+ Bases very often have OH- (“hydroxide”) How to remember??? In the alphabet, “H” comes before “O”, just like “acids” come before “bases
A substance has a pH of 8. What is it likely to contain more of? O2 K H+ OH- A pH of 8 means….. It’s a BASE so…. It contains ….. OH-
Water Think of water as an H+ bonded with an OH-. H2O (two hydrogen, one oxygen) Equal acid and base. Therefore…. Pure water is neutral with a pH of 7
Which makes water very important… Some things dissolve better in acids. Some things dissolve better in bases. Water is a universal solvent.
O H Acid, H+ Base, OH- H Rather like the Earth has a North Pole and a South Pole, water is POLAR, with a more “acid / +” pole and a more “base / -” pole. That’s why it’s called a UNIVERSAL SOLVENT.
This is how water easily breaks apart ionic compounds. It surrounds both negative and positive ions and breaks apart ionic solids.
One reason water is an effective solvent is that it- • Contains the acid, H+ • Can evaporate easily • Is a polar molecule • Contains the base, OH- The correct answer is “c”.
Physical vs Chemical Changes Ice melting Iron rusting Food digesting in your stomach Wood burning Body decomposing Sugar dissolving
Which of these describes a pollution-producing process that involves only a physical change? • Coal with a high sulfur content is burned, producing gases that cause acid rain. • Chlorofluorocarbons are released, changing ozone in the upper atmosphere into oxygen. • Hot wastewater is discharged into a lake. • Nitrogen oxide emissions combine with water vapor, producing nitric acid. The correct answer is “c”
Solubility of a solid in a liquid a measure of how much solute will dissolve into the solvent Temperature will affect solubility- the solubility will be INCREASED as the temperature is increased. Stirring will increase solubility. Molecular or Particle Size will affect the solubility. The larger the molecule or particle the less soluble the substance will be. So smashing something into smaller pieces makes it dissolve better.
Solubility of a gas in a liquidThink of carbonation in your soft drink! Pressure will affect solubility of a gas in a liquid. As the outside pressure goes up, the solubility (staying dissolved) will go up. For example: the CO2 (fizzies) stays dissolved in your coke because it’s bottled under high pressure. Once you open the lid, the bubbles began to escape. Higher pressure increases solubility. Temperature affects the solubility. Cokes lose their fizziness faster as the temperature increases. Colder temperature increases solubility.
Decompression sickness can happen in these situations: -A diver ascends too quickly from a dive -An unpressurized aircraft goes too high. -The cabin pressurization system of a high-flying aircraft fails. -Divers flying in any aircraft shortly after diving. -An astronaut exits a space vehicle to perform a space-walk. These situations cause inert gases, generally nitrogen, which are normally dissolved in body fluids and tissues, to come out of physical solution (“outgas”) and form gas bubbles. If nitrogen is forced to come out of solution too quickly, bubbles form in parts of the body causing the signs and symptoms of the "bends" which can be itching skin and rashes, joint pain, sensory system failure, paralysis, and death.
As a scuba diver goes deeper underwater, the diver must be aware that the increased pressure affects the human body by increasing the- • body’s temperature • Amount of dissolved gases in the body • Amount of suspended solids in the body • Concentration of minerals in the body The correct answer is “b”
All of these can affect the rate at which a solid dissolves in water except • Decreasing air pressure • Stirring the water • Increasing the temperature of the water • Using larger crystals of the solid The correct answer is A, decreasing the pressure in the air above the water won’t affect the rate the solid dissolves
Bonding Ions will bond to form neutral molecules. What’s the chemical formula for Aluminum Hydroxide formed when Al+3 bonds with OH- ? Just “cross-multiple” the numbers! Al(OH)3
Let’s try some: Zn2+ and Cl ZnCl2 Al3+and SO42- Al2(SO4)3 Ca1+ and CO31- CaCO3 Fe3+ and SO42- Fe2(SO4)3 NH4+ and PO43- (NH4)3PO4
Conservation of Mass According to the law of conservation of mass, the total mass before a reaction is equal to the total mass after the reaction. Total mass before = total mass after
Conservation of Mass For example: In this reaction, how much zinc was present in the zinc carbonate? 64 g Calcium + 192 g Zinc Carbonate 152 g Calcium carbonate + ?? g Zinc Think of the as an = 64 + 192 = 152 + ?? There was 104 g of Zinc
3 g of CaCl2 reacted with 2 g of Na3PO4 the products were 1 g of Ca3(PO4)2 and table salt- NaCl. How many grams of NaCl were produced?
