Transcript Chapter 2
Bellringer – November 12, 2014 Look at the Periodic Table: 1)What does the Au stand for? 2)What atomic number is aluminum and what is it’s symbol? 3)What 6 elements are WE mostly made up of? Look at the periodic table and take a guess! Chemistry Introduction to Chemistry Honors Biology Ms. Kim Composition of Matter • Matter - everything in universe is composed of matter (“stuff”) – Matter is anything that occupies space or has mass • Mass – quantity of matter an object has • Weight – pull of gravity on an object Chemistry of Life • All matter is composed of tiny particles called atoms. • There are 109 types of atoms - a substance made up of one kind of atom is called an element. • An atom is the smallest part of an element that still has the properties of that element. Atomic Structure Each atom is made up of smaller parts called protons, electrons and neutrons. Protons and neutrons are found in the central portion of the atom called the nucleus. Protons (+) in nucleus Neutrons (0) in nucleus Electrons (-) in a cloud outside! There are SIX elements necessary for life – C – Carbon H – Hydrogen N – Nitrogen O – Oxygen P – Phosphorous S- Sulfur CHNOPS •The most important element is CARBON! Elements Therefore…. • Elemental Symbol – Unique one/two letter symbol Protons + Neutrons = Mass # Mass # - Atomic # = Neutrons • Atomic # of a neutral element – Equals the # of protons AND the # of electrons – Unique for each element • Atomic Mass #– Avg. mass of an atom of the element (AMU) – Equals the SUM of protons and neutrons The Nucleus Middle of the atom (central core) Holds positive charged protons and neutral neutrons Positively charged Contains most of the mass of the atom The Protons • All atoms of a given element have the same number of protons • #of protons = the atomic number • # of protons (+’s) = # of electrons (-’s) (in a neutral atom) The Neutrons • The number varies slightly among atoms of the same element • Different number of neutrons produces isotopes of the same element Isotopes \ Isomers •Isotopes = an element with the same # protons, but different # neutrons – Ex: C-12 vs. C-14 •Isomers = compounds with the same molecular formula, but different structures Practice Problems! 1. How many protons does a sodium (Na) atom have? 2. How many neutrons does a fluorine (F) atom have? 3. What is the atomic mass for oxygen (O)? 4. What is the atomic number for phosphorus (P)? The Electrons Negatively charged high energy particles with little or no mass Travel at very high speeds in different energy levels Energy levels are different distances from the nucleus Electron Shell Electron Shell • Shells: – Inner most can hold at most 2 e– Outer most can hold at most 8 e– Third outer most can hold at most 8 e• Elements want to have full shells, because this makes them stable! • The electrons on the most outer shell is called VALENCE electrons • EXAMPLE: Carbon (neutral) – Atomic # = 6 6 total electrons • • • • 2 electrons fill the inner most shell 4 will be in the outer most shell This means Carbon has 4 VALENCE electrons Can bond to 4 other atoms! Periodic Table • Elements are arranged by their atomic number on the Periodic Table • The horizontal rows are called Periods & tell the number of energy levels • Vertical groups are called Families & tell the outermost number of electrons Molecules and Compounds • Molecules – 2+ atoms bonded together – O2 for Oxygen • Compound – 2+ elements bonded together - CO2 for carbon dioxide and NaCl for sodium chloride Compounds • Compounds : Examples – – – – – Have different properties than individual elements Ex: NaCl = 1 sodium + 1 chloride table salt Ex: H20 = 2 hydrogen + 1 oxygen water Ex: NaOH = 1 sodium + 1 oxygen + 1 hydrogen Ex: CO2 = 1 carbon + 2 oxygen Compounds • What happens when the ratio of atoms changes? H20 vs. H2O2 • When the ratio of elements in a compound changes, the physical and chemical properties change too Molecules • Molecule is two or more atoms held together by covalent bonds. Almost all of the substances that make up organisms, from lipids to nucleic acids to water, are molecules held together by covalent bonds. • A compound is a type of molecule. All compounds are molecules, but all molecules are NOT compounds. • Molecule Examples: H2O, O2, O3 • Compound Examples: NaCl, H2O Bonds Molecular “glue” Holds atoms together to form compounds Valence electrons are involved in bonding Valence electrons = electrons on outer most energy level. Atoms are most stable when their outer most energy level is filled • What holds atoms together? – Atoms are held together by chemical bonds • Goal: to fill outer electron shell…so atoms BOND together (share or give away/take electrons) to get a full outer shell • 3 main types: – Ionic bonds – Covalent bonds – Hydrogen bonds Covalent Bonding • Formed when two atoms SHARE one or more pairs of electrons. (‘co’ means ‘together’) • When two or more atoms are joined by covalent bonds, we call this a molecule – Covalent bonds are Very strong • Because positive and negative electrical charges attract each other ionic bonds form Ionic Bonds • Formed when one or more electrons are transferred from one atom to another • Atoms lose or gain electrons – If an atom loses electrons becomes positively charged (+) – If an atom gains electrons becomes negatively charged (-) • Atoms that have gained or have lost electrons are ions – Ex: Salt (NaCl) Cations & Anions • Cation = when an atom loses an electron, it becomes more positively charged – Positive Ion = Cation – Remember: Cats have PAWS and are POSITIVE – Ex: Removing an electron from a K (potassium) atom will….create a POSTITIVE ION = CATION • Anion = When an atom gains an electron, it becomes more negatively charged – Negative Ion = Anion – Ex: If a Cl (chlorine) atom gains an electron…creates a NEGATIVE ION = ANION States of Matter • Atoms are in constant motion (called kinetic energy) • The rate at which atoms or molecules in a substance move determines its state Level of Organization Subatomic particles (p+, e-, n0) atom (O) Element (O) molecule (O2) macromolecules (lipid) Cell (blood cell) <--life begins here Tissue (epithelia tissue) Organ (lung) Organ system (Respiratory System) Organism (Panthera leo (lion))