-Only 88 of the 115 elements occur naturally. The rest have been created in labs.
– Oxygen seems to be the most abundant element found on Earth.
– SYMBOLS FOR ELEMENTS
– Element names are derived from German, Latin or Greek words that describe the properties of retain elements.
-It’s also very common for elements to be named for the place where it was discovered, Ex: Californium.
– Some are also named after famous scientists. Ex: Einsteinium
– We also use abbreviations for a lot of elements, aka elements symbol.
– Daltons AtomicTheory
Facts about all atoms:
1. Most natural materials are mixtures of pure substances.
2. Pure substances are either elements or compounds.
3. A given compound always contains the same proportions (by mass) of the elements. For example, water always contains 8 g of oxygen for every 1 g of hydrogen. And carbon dioxide always contains 2.7g of oxygen for every 1g of carbon. Principle is called law of constant composition. It basically means that a given compound always has the same composition.
– John Dalton, English scientist, was aware of the observations and in 1808 he came up with an explanation called Dalton’s Atomic Theory,
-Dalton’s Atomic Theory:
1 Elements are made of tiny particles called atoms.
2 All atoms in a given element are identical.
3 Atoms of a given element are different from those found in any other element.
4 Atoms of one element can combine with atoms of other elements to for compound. A given compound has the same relative numbers and types of atoms.
5 Atoms are indivisible in chemical processes.
– Dalon’s model explains the observations clearly.
-Dalton was able to correctly the formation of multiple compounds between to elementsl
-Compounds contain the same relative mass,
A compound contains the same relative numbers of atoms for each element.
– types, and number of each type of atom is expressed with a chemical formula.
– J. J. Thomson showed that atoms of any element can emit tiny negative particles. He could show that they were repelled by a negative part of an electric field.
– He concluded that all types of atoms must contain negative particles, now called electrons Thomson thought that the atom must contain positive particles that balanced the negative charges giving the atom an overall zero charge.
– Lord Kevin thought an atom was like a pudding of positive charge with enough electrons to balance the effect,
– 1911, Ernest Rutherford noticed that alpha particles will sometimes be deflected by something in the air. Rutherford begins his experiment by directing an alpha particle toward metal foil. The foil was surrounded by detectors that would light up with the presence of alpha particles. While some alpha particles asked through the foil, many were deflected. This disproves the pudding model because if the pudding model was correct, all the alpha particles should have crashed through the metal foil.
-Rutherford thought that the results could only be explained by nuclear atom., an atom with a dense positive charge (nucleus) around which the tiny electrons move. Rutherford says that nucleus had a positive charge, Rutherford 1919 conclude that the nucleus must contain an atom called portion. Proton has a positive charge.,
– Protons = 1+” Electrons 1-
-Rutherford and his Co worker will later discover the neutron inside the nuclei with has no charge.
– 10^-13 is the nucleus, Electrons move about the nucleus with a distance of about 10^-8cm.
-The nucleus has the proton, which have a positive charge which is equal to the magnitude of a negative charge and the neutron (which has the same mass as a proton and no charge.
– Isotopes are atoms with the same number of protons and Electrons, but different number of neutrons.
-The number of protons in an atom can be found by looking at it’s atomic number. The sum of the number of protons and the number of neutrons is the mass number.
– The periodic table can be split into 5 groups, alkali metal, alkaline earth metals, halogens, noble gases, and transition metals.
– OPhysical Properties of Metals
1 Efficient conductors of heat and electricity.
2 Malleability *can be hammered into thin sheets)
3 ductility (pulled into wires)
4 A lustrous (shiny) appearance
Element table: Everything other than Hydrogen on the Alkaline metal through transitive metals side are metal. Hydrogen and most on the right are Nonmetals. The Staircase are metalloids.
-Gold, silver, and platinum are part of noble metals.
-Diatomic molecule made up of two atoms.
-neutral entity – zero net charge
-We can create ions by taking a neutral atom and adding/taking one or more .
Section 11.4 Energy levels of Hydrogen
– Atoms with excessive energy is in an excitment state.
– Excited atoms release some/all of it’s Excited energy by emmiting photons and moving back to lower energy levels (aka Ground state).
– Hydrogen atoms absorb energy from outside source ~Hydrogen atoms gets excited ~then the atom goes back to groundstage with photos light.
– The energy that goes into a Hydrogen atom is equal to the photos emitted.
– Hydrogen have different excited states based on amount of energy that goes in.
– Energy levels are quatized. All atoms are quatized.
– Quatized: Only certain levels allowed.
– it was believe before, atoms can live at any energy level. This turns out to not be true.
-Matter: the stuff that composes everything in the world.
-Matter has mass and it occupies space.
-There are three different states of matter: solid, liquid, and gas.
-physical properties of a substance include odor, color, volume, and state (gas, liquid, solid) density, melting point, and boiling point.
– Chemical properties (the ability to for new substances).
-Chemical property example: burning of wood, rusting of metal, digestion of food, and the growth of grass.
– Usually chemical changes give substance changes to a different substance or different substances. For example, in the case of burning wood, heat is given off and it leaves a residue of ashes.
– Matter can undergo changes to both its physical and chemical properties.
– Physical changes do not affect the composition of the substance. Ex: H2O can be found in three different states, solid (ice), liquid (water) , and gas (steam). In each state the chemical composition stays the same.
– Chemical changes involve a change in the fundamental components of the substance. Chemical changes are called reactions.
– Elements are substances that can not be broken down into other substances through chemical means.
– Examples of elements are oxygen (O), hydrogen (H) and Helium (He).
– Certain elements can bind together to for compounds, or substances that have the same composition of atoms.
– Compounds are made of elements and therefore can be broken down into elements.
– Official definition of compound: A substance made of a combination of elements that can be broken down into those elements through chemical means.
– Water is an example of a compound, it’s made of a combination of a hydrogen molecule and two oxygen molecules.
– Compound ALWAYS contains atoms of a different atom.
-A compound contains more than one type of atom but always has the same composition.
-Mixtures of substances
– A mixture has a variable composition (it’s composition often varies.
– Example: Coffee, trees, wine and tap water (which includes h2o and other minerals.)
-Pure substances has the same composition.
-Pure substances = element/compound.
-Example: Distilled water. While water from the sink can contain minerals and such, Distilled water
only has pure h2o molecules.
-mixtures can be separated into two or more pure substances (elements/compounds.)
– mixtures can be classified into two different categories. Homogeneous and heterogeneous.
– Homogeneous mixtures are same throughout Example: A mixture of salt and water will eventually result in a liquid that has the same properties throughout. A homogeneous mixture can also be called a solution.
-Other example – Brass and air.
-Heterogeneous mixtures are mixtures that contain regions with different properties when compared to other regions. Example: A mixture of sand and water is heterogeneous cause the liquid divides into regions with just sand and regions with just water. Different regions in one mixture = heterogeneous.
-Separation of mixtures.
– matter found in nature are usually a mix of pure substances.
– Distillation is a method used to separate mixtures back into their pure substance forms. Example: Sat water is boiled into gaseous state and then turned back to a liquid. Water turns into steam and the junk remain as solids. The steam turns back into the water except without the minerals (which are now solid).
-Filtration is another method. In Filtration a mesh, like filter paper is used. The liquid passes through but leave behind the solids.