Presentation on theme: "What science do you see?. 2-1 Chemistry of life Objectives Define matter Explain the relationship between elements and atoms Draw and label a model of."— Presentation transcript:
Objectives Define matter Explain the relationship between elements and atoms Draw and label a model of the structure of an atom Explain how compound affect an atom’s stability Contrast covalent and Ionic bonds
Matter Matter: takes up space, has mass Mass: how much of something there is Element: simplest form of matter –Can’t be broken down with chemical means –If you have a lump of copper, boiling or freezing doesn’t change it There’s about 118 elements
When we total the monetary value of the elements in our bodies and the value of the average person's skin, we arrive at a net worth of $4.50 Our most valuable asset is our skin. The method the Imperial State Institute for Nutrition at Tokyo developed for measuring the amount of a person's skin is to take a naked person, and to apply a strong, thin paper to every surface of his body. After drying, its removed, cut it into small pieces, and the person's measurements are totaled.The average person has fourteen to eighteen square feet of skin, (variables being height, weight, and breast size). Based on the selling price of cowhide,( approximately $.25/ square foot), the value of an average person's skin is about $3.50. On the other hand consider that urban legend of drugged travelers awaken in ice- filled bathtubs only to discover one of their kidneys has been harvested by organ thieves. Though: in real life a small village in India was reportedly nicknamed Kidney Village by national geographic writers because so many of its inhabitants had voluntarily sold kidney’s for 800$ How much would you pay if you had to wait? Now the question to ponder is this: Is the whole worth more than the sum of the parts? If you put these these powdered elements together in a blender; how long would you have to leave it on for to get a human? How do these elements interact to make you who you are?
Dalton’s atomic theory All elements are made of atoms Atoms of the same element are identical –Atoms of dif. Elements are dif. Atoms of different elements can combine in whole number ratios to form compounds Reactions occur when atoms separate join & rearrange –Atoms them selves are never changed
Whole number ratios are like two to one for H 2 O. Or one two to three for Iron Sulfide Fe 2 S 3 Dalton’s born to a family of poor Quakers, Same city William Wordsworth comes from, Bright guy, at the age of 12 the put him in charge of the local school He was color blind and the world called it Daltonism for a while. Of course not much can happen without somebody objecting, in this case it was Ernst Mach (for who we named the speed of sound) The theory came out in his 1808 book, and it was like saying I’ve found a new planet. But he kept his job as a teacher, and visiting scientists from around the world would have to wait while he finished teaching math class. Hugely popular, forty thousand people attended his funeral in 1844.
Just how small is an atom? Small enough so that light will miss it 50 million atoms would fit side by side in a 1cm long groove so to speak. Scanning electron microscopes can view the surface of atoms
Subatomic Particles ParticleSymbol Charge Relative Mass Electron e - 1- 0 Proton p + + 1 Neutron n0 1
Planetary Models of Elements p + represents protons, n o represents neutrons
Atomic Number on the Periodic Table 11 Na Atomic Number Symbol
Number of Electrons An atom is neutral The net charge is zero Number of protons = Number of electrons Atomic number = Number of electrons
Isotopes Atoms with the same number of protons, but different numbers of neutrons. Atoms of the same element (same atomic number) with different mass numbers Isotopes of chlorine 35 Cl 37 Cl17 chlorine - 35 chlorine - 37
Isotopes and Radioactivity Isotopes –elements that differ in the number of neutrons 1 H, 2 H, 3 H; hydrogen, deutrium, tritium –extra neutrons result in increased atomic weight “heavy water” –have no change in chemical behavior same valence electrons Atomic weight –Average atomic mass of the mixture of isotopes of an element found in a sample
Octet Rule Noble gases are stable because they have just the right number of valence electrons. 2 for helium 8 for the rest This balances them eneregetically Octet Rule: all elements try to form bonds so they have 8 valence electrons –Some try to have just 2
Ions When an atom gains or loses an electron it takes on a negative or positive charge If you gain an electron (negative energy) you have a negative charge = Anion –Plus a negative is subtraction – Cl - If you lose an electron (negative energy) you have a positive charge = Cation –Minus a negative is addition – Na +
Electrons can be transferred Sodium has 1 valence electron Chlorine has 7 valence electrons How can Chlorine achieve the octet? –It gained an electron giving it a negative charge –It resembles a noble gas Did Sodium achieve the octet? –It now resembles neon
Salt In Ancient Rome, salt started to be used as money originating the current Latin-derivative term salary. Payments to Roman workers were made in salt. Morton’s Salt: "When it rains, it pours“ –Owned by Rohm & Hass –#286 on fortune 500 –7.99 Bil –They make all kinds of stuff Iodized Salt
Ions attract each other Opposites attract Ionic bonds between ions, they are trading electrons. Ionic compounds have ionic bonds –Crystals form –Stable so they have high melting points –Don’t bend –Shatter
Electrons can be shared: Covalent Bonds H 2 O is not ionic like NaCl It becomes stable like noble gases in a different way. In water the Hs and O share electrons –It’s a different kind of attraction
Covalent bonds Covalent compounds have covalent bonds 1 unit of a covalent compound is called a molecule –Sometimes they are called molecular compounds They have lower melting points Examples: Water, Carbon Dioxide, Sugar, Gasoline, Wax, Lighter fluid, propane
1.What is matter? Anything that has mass and takes up space
2.What is the relationship between elements and atoms? Elements are substances that can’t be broken down into simpler kinds of matter Atoms are the smallest particle of an element that retains all the properties of that element
3.Describe the arrangement within energy levels of the six electrons in a carbon atom. Carbon will have 2 electrons in the first energy level and four electrons in the second level How many valence electrons does carbon have to share with other atoms?
4. How are isotopes of the same element alike? They have the same atomic number and the same number of protons.
5.How can we predict which elements are reactive under normal conditions and which are unreactive? Whether or not their outer level of electrons is filled.
6. Distinguish between ionic and covalent bonds. Covalent: Sharing electrons Ionic: Trading electrons
7.Why are mass and weight two different terms? Mass describes how much matter is in an element Weight takes gravity into consideration.