CHEMICAL ELEMENTS AND COMPOUNDS MATTER: made of chemical elements and compounds WHAT IS MATTER? MASS V. WEIGHT MASS- THE AMOUNT OF MATTER IN AN OBJECT WEIGHT-A MEASURE OF HOW STRONGLY AN OBJECT IS PULLED BY EARTH’S GRAVITY-VARIES WITH DISTANCE FROM EARTH’S CENTER Are your mass and weight the same????

ELEMENTS FOR LIFE C O H N LIFE requires about 25 elements C,O,H,N- make up 96% of living matter ELEMENTS-made up of all the same type of atoms COMPOUNDS-made of diff. Elements C O H N

ATOMS AND MOLECULES ATOM-smallest unit of matter 3 particles in an atom: Proton (+) Neutron(0) Electron(-) **IF AN ATOM IS ELECTRICALLY NEUTRAL, THE # OF PROTONS = # OF ELECTRONS

ATOMIC NUMBER & ATOMIC WEIGHT ATOMIC #= # of protons and electrons in an atom- lefthand lower subscript ATOMIC MASS= # of protons and neutrons in an atom-lefthand superscript WHAT IS THE ATOMIC MASS OF SODIUM??? 23 Na 11

ISOTOPES ISOTOPES-atoms of an element have the same atomic number but different atomic masses They have the same number of protons, different number of neutrons Some isotopes are radioactive;these are unstable atoms in which the nucleus decays emitting subatomic particles and/or energy as radioactivity Half-life: time for 50% of radioactive atoms in a sample to decay

The energy level of electrons Electrons-negatively charged particles Energy-ability to do work Potential energy-stored enegy Electrons with the lowest potential energy are closest to the nucleus Electrons gain energy as they move away from the nucleus

Energy con’t Electrons may move from one energy level to another-they gain or lose energy equal to the difference in potential Energy between the old and new energy level

ELECTRON ORBITALS ORBITAL-3d space where electrons are found the majority of the time

ENERGY LEVELS FIRST ENERGY LEVEL -has one “s” orbital Holds a max of 2 electrons SECOND ENERGY LEVEL -has one “s” orbital and 3 “p” orbitals -holds a max of 8 electrons HIGHER ENERGY LEVELS -has S AND P ORBITALS

ELECTRON CONFIGURATIONS

CHEMICAL PROPERTIES OF AN ATOM VALENCE ELECTRONS-the electrons in the outermost shell. They determine how an atom will react OCTET RULE - valence shell is complete when it contains eight electrons *** if an atom does not have a full outer shell it is reactive and will form bonds with other unstable atoms

CHEMICAL BONDING CHEMICAL BONDS-attractions that hold molecules together 1) COVALENT BONDS-formed by atoms that SHARE electrons--these are STRONG bonds

BONDING SINGLE COVALENT BOND-sharing of a single pair of valence electrons DOUBLE COVALENT BOND-sharing of two pairs of valence electrons COMPOUND-A substance made of 2 or more elements combined in a fixed ratio Ex: water (H20) , methane(CH4)

COVALENT BONDING

POLAR AND NONPOLAR COVALENT BONDS ELECTRONEGATVITY- an atom’s ability to attract and hold electrons The more electronegative an atom, the more strongly it attracts shared electrons Scale determined by Linus Pauling: O - 3.5 S and C - 2.5 N - 3.0 P and H - 2.1 NONPOLAR COVALENT BOND-fomed by an equal sharing of electrons-when electroneg of both atoms is about the same

POLAR COVALENT BONDS COVALENT BONDS FORMED BY AN UNEQUAL SHARING OF ELECTRONS CHECK OUT THE NEXT EXAMPLE OF A WATER MOLECULE THE OXYGEN IS STRONG ELECTRONEG., SO ELECRONS SPEND MORE TIME AROUND THE OXYGEN THAN THE HYDROGENS THIS GIVE THE OYGEN A SLIGHT NEG CHARGE AND THE HYDROGENS A SLIGHT POSITIVE CHARGE

POLAR COVALENT BONDS

POLAR AND NONPOLAR COVALENT BONDS

IONIC BONDS ION-charged atom or molecule ANION-an atom that has gained one or more electrons and as become negatively charged CATION-an atom that as lost one or more electrons and has become positively charged

IONIC BONDING IONIC BOND- bond formed by the electrostatic attraction after the transfer of an electron from one atom to another OPPOSITIES ATTRACT-opposite charged of the atoms create the ionic bond IONIC COMPOUNDS-are called salts-will dissolved easily in water

IONIC BONDS

WEAK BONDS IMPORTANT IN CELL CHEMISTRY BIOLOGICALLY IMPORTANT WEAK BONDS INCLUDE: HYDROGEN BONDS, IONIC BONDS THEY MAKE CHEMICAL SIGNALLING POSSIBLE IN LIVING ORGANISMS BECAUSE THEY ARE ONLY TEMPORARY ASSOCIATIONS CAN FORM BETWEEN MOLECULES OR BETWEEN DIFF PARTS OF A SINGLE LARGE MOLECULE HELP STABILIZE THE 3-d SHAPE OF LARGE MOLECULES (DNA AND PROTEINS)

HYDROGEN BONDS HYDROGEN BONDS-formed by the charge attraction when a H+ atom covalently bonded to one atoms is attracted to another atom A weak bond Is a charge attraction between oppositely charged portions of polar molecules VAN DER WAALS INTERACTIONS Weak interactions that occur between atoms and molecules that are very close together and result from charge symmetry in electron clouds

HYDROGEN BONDING IN DNA HYDROGEN BONDING IS AT THE VERY BASIS OF THE HUMAN GENOME

MOLECULAR FUNCTION IS RELATED TO SHAPE A molecule has a characteristic size and shape The function of many molecules depends on its shape Ex:: Insulin causes glucose uptake into liver and muscle cells because the shape of insulin molecule is recognized by specific receptors on the target cell

MOLECULER SHAPE RELATES TO ITS FUNCTION

CHEMICAL RXNS MAKE AND BREAK CHEMICAL BONDS CHEMICAL REACTIONS-the process of making and breaking chemical bonds leading to changed in matter Process where reactants undergo changes into products Matter is conserved and reactants are only rearranged to form products Most reactions are reversible CHEMICAL EQUILIBRIUM-when forward and reverse rates of reactions are equal