Chemistry Draw a Bohr Model of a carbon atom. (Turn to page 269 of your textbook.)

List common elements & chemical symbols. Example: Carbon C Chemistry List common elements & chemical symbols. Example: Carbon C

List common elements & chemical symbols. Chemistry List common elements & chemical symbols. Example: Carbon C Hydrogen H Oxygen O Carbon C Iron Fe Sodium Na Magnesium Mg

Identify Chemicals Chemical: substance used in or formed by a chemical process. Synthetic Chemical: a chemical that is not formed in nature and is made by people. Matter: anything that has mass and volume. Element: a substance that cannot be broken down into simpler substances by ordinary chemical means. Synthetic element: elements that are made by scientists in a laboratory and do not exist in nature. Mixture: a type of matter that forms when two or more substances are combined but do not join together chemically. Compound: a type of matter that forms when two or more elements combine chemically.

Chemicals

Compounds Molecule: the smallest unit of a compound that has all the properties of the compound. Chemical Formula: uses chemical symbols and subscripts to identify the number of atoms of each element in a molecule of a compound. Example: H2O is water. Atom: the smallest unit of an element that has all the properties of the element. Proton: a particle with a positive charge.

Compounds Neutron: neutral particle, does not have a charge. Electron: has a negative charge. Nucleus: central core made of protons and neutrons. Valence Electrons: electrons in the outermost energy level of an atom. Ionic bonds: bonds formed by the transfer of electrons. Ion: an atom that has gained or lost one of more electrons. Covalent bond: formed when two atoms share electrons.

What is a compound? A compound is a pure substance that is created by 2 or more elements chemically reacting and joining together Ex: NaCl, H2O, CO2, NH3, NaHCO3, and C6H12O6 Compounds form to allow elements to become more stable Na is flammable when it comes in contact with H2O, and Cl2 is a toxic gas NaCl is a very stable compound that is neither flammable nor toxic (in normal quantities)

What is a mixture? A mixture is the physical combination of 2 or more substances It is important to understand that a mixture is not chemically combined Mixtures can be separated by physical means such as filtration, distillation, and chromatography Remember no chemical change is occurring

What is a mixture? Homogeneous mixtures are commonly called solutions. Solution = Solute + Solvent Solute: “stuff” being dissolved Solvent: “stuff” doing the dissolving The solvent is present in greater quantity The solute is present in the lesser quantity Ex: Salt water: Salt=solute, Water=solvent

How is it all related? Protons Electrons Neutrons Atoms Matter

What are properties? Property: a characteristic of a substance that can be observed Physical property: a property that can be observed without changing the identity of the substance. Luster malleability: the ability to be hammered into a thin sheet ductility: the ability to be stretched into a wire Magnetism Electrical/thermal conductivity Solubility

Special Physical properties Melting point: the temperature at which a substance changes from a solid to a liquid at a given pressure water = 0oC Boiling point: the temperature at which a substance changes from a liquid to a gas at a given pressure water = 100oC Density is the amount of mass per unit of volume. Density, melting point, and boiling point can be used to identify a substance. The density of water is 1.0g/mL

Chemical Properties Chemical property: a property that can only be observed by changing the identity of the substance Examples: flammability ability to rust reactivity with vinegar

Changes Physical change: a change that occurs that does not change the identity of the substance Melting ice(change in state or phase) Freezing Kool-aid Tearing paper Boiling water (same as melting ice) Chemical change: a change that occurs causing the identity of the substance to change Burning Digesting food Reacting with other substances A chemical change is called a chemical reaction

Chemical Changes Indicators of a chemical change: Evolution of light Evolution of heat Evolution of a gas Color change Formation of a precipitate (solid that forms from a chemical reaction) Chemical reaction (also known as a chemical change) is a change in a substance or substances that results in a totally new substance Ex: 2H2(g) + O2(g)  2H2O(g) Notice that the reactants (the substances you start with) combine to form a new substance (the product)

Chemical Reaction It is important to understand that when matter undergoes a chemical reaction (ie, a chemical change) it does not disappear or appear The atoms are rearranged and form new bonds, but no matter is lost nor gained This is called the Law of Conservation of Matter Therefore, if you start with 10 atoms of oxygen, you must end with 10 atoms.

The Atomic Theory Key Ideas Explanation All matter is composed of atoms. Atoms of a given element are identical. Atoms of different elements combine in simple whole-number ratios to form chemical compounds. Explanation Atoms are the building blocks of matter. All atoms of the same element have the same number of protons and electrons. The ways atoms combine to form compounds is determined by the valence electrons of an element.

What are atoms? Atoms are the building blocks of matter Atoms are too small in size to study easily Size of Earth : soda can = soda can : atom The nucleus contains protons (positive charged) and neutrons (no charge). The nucleus is surrounded by the electron (negative charge) cloud.

What are atoms? Protons and neutrons live compacted in the tiny positively charged nucleus accounting for most of the mass of the atom The negatively charged electrons are small and have a relatively small mass but occupy a large volume of space outside the nucleus

Balance In an atom: The protons = the electrons If 20 protons are present in an atom then 20 electrons are there to balance the overall charge of the atom—atoms are neutral The neutrons have no charge; therefore they do not have to equal the number of protons or electrons

Balance Atomic number: this number indicates the number of protons in an atom Ex: Hydrogen’s atomic number is 1 So hydrogen has 1 proton Ex: Carbon’s atomic number is 6 So carbon has 6 protons **The number of protons identifies the atom. Ex. 2 protons = He, 29 protons = Cu

Atoms Mass number: the number of protons and neutrons in the nucleus Ex: hydrogen can have a mass of 3. Since it has 1 proton it must have 2 neutrons # of neutrons = mass # - atomic # The electrons are equal to the number of protons So e- = p = atomic # Ex: He has a mass # of 4 and an atomic # of 2 p+ = 2 no = 2 e- = 2

Bohr Model Bohr Model of the atom: All of the protons and the neutrons The 3rd ring can hold up to 18 e- The 1st ring can hold up to 2 e- The 4th ring and any after can hold up to 32 e- The 2nd ring can hold up to 8 e-

Periodic Table Atomic mass: is equal to the number of protons and neutrons in the nucleus of one atom of the element. Periodic table: a chart that organizes information about all of the known elements according to their properties. Atomic number: the number of protons contained in each nucleus of its atom.

Periodic Table Period: horizontal row in the periodic table. Group: Vertical column on the periodic table or chemical family. Reactivity: how likely an element is to form bonds with other elements. Metalloids: elements that have some properties of both metals and nonmetals. Inert: unable to react chemically.

Block of Periodic Table Label the different parts. 2 He 4.0026 Helium

Labeled Element 2 He 4.0026 Helium Elemental Symbol Atomic Number = # of protons Atomic Mass = # of protons plus neutrons

Periodic Table http://www.accessscience.com/periodicTable.aspx Only nonmetal on the metal side Nonmetals are on the right of the stair-step Metals are to the left of the stair- step Semi-metals, “metalloids,” touch the stair-step http://www.accessscience.com/periodicTable.aspx

Properties of Metals and Nonmetals Properties of Nonmetals Most are gases, except bromine, which is a liquid. Are brittle in the solid phase Have a tendency to be dull, not shiny and bright Are poor conductors of heat and electricity Tend to gain electrons in chemical reactions Properties of Metals Solid at room temperature, except mercury, which is a liquid Malleable and ductile Have luster- are shiny High conductivity- are good conductors of electricity and heat Tend to lose electrons in chemical reactions

Groups Group 1- Alkali metals, easily combine with nonmetals, have one valence electron. Group 2- Alkaline Earth metals, reactivity but not as reactive as group one, two valence electrons, reactivity increases with increasing atomic number. Group 3-12- Transition Metals, generally hard solids with high melting points. Group 13-16- First element in column is the name of that group, subtract 10 from group number to get number of valence electrons. Group 17- Halogens, most reactive nonmetals, reactivity increases as atomic number decreases. Group 18- Noble gases, least reactive, will form compounds under extreme conditions (except Helium).

Types of Bonds Covalent Bonds Atoms seek to have 8 valence electrons in outer level, so they share electrons. Forms a molecule of nonmetals only. A molecule can be made up of atoms of the same element or atoms of different elements. For example Cl2 or H2O. Ionic Bonds Atom that loses electrons becomes a positive ion. Atom that gains electrons becomes a negative ion. Bond between metal and nonmetals. Example: Sodium Chloride (NaCl)

Periodic Table Challenge How many words can you make using the chemical symbols in the Periodic Table? You may use the symbols more than once in a word, but you cannot mix up the letters. The symbols must be used as they appear in the Periodic Table. You may also use words with only one or two letters as well as the names of people, places, and other elements. You must provide the symbols (in correct format) as well as the word. Examples: He + At = Heat N + O + B + O + Dy = Nobody