CHEMISTRY OF LIFE. Composition of Matter. Composition of Matter 10/3/14

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1 CHEMISTRY OF LIFE Matter- occupies space and has mass Mass- the quantity of matter an object has Weight- the quantity of matter multiplied by the gravity of the planet you are on. Earth s gravity is 9.8 m/s 2 Sun s gravity is 274 m/s 2 In order to convert pounds to kilograms you multiply.45 to pounds n Ex. 170lbs x.45kg/lbs = 76.5kg Now calculate your mass and then your weight on Earth and the Sun Atoms The simplest particle of an element Atoms contain subparticles called protons, neutrons and electrons n Protons are positively charged particles that have mass n Electrons are negatively charged particles, but very little mass n Neutrons do not have a charge and have mass equal to protons Have a defined structure and the element can be determined by that structure 1

2 Atomic structure Nucleus Energy Levels Elements- pure substances that cannot be broken down into simpler forms of matter through chemical processes They have been represented on the periodic table in this form: 8 O 16 Atomic Number Symbol Atomic Mass Periodic Table Atomic Number is the same as the number of protons in an element n The number of protons determines what element it is The symbol represents the name of the element n O is the symbol for Oxygen Atomic Mass is the protons plus the neutrons n If you subtract the atomic number from the atomic mass it will give the number of neutrons in the nucleus 2

3 Families/groups Valence Periods Periodic Table Families/Groups n Increase in size as you go down the column n Elements react in similar manners Periods n Increase in size as you go from left to right n Number of valence electrons increases from left to right Valence n Number of electrons in the outer most energy level So how do you draw an atom? Bohr Diagram Model of the atom with the nucleus drawn in the center and the energy levels drawn on the out side 8P + 8N 3

4 Bohr diagram The first energy level can only have 2 electrons The second energy level can only have 8 electrons The third energy level can have up to 18 electrons n Argon with only 8 electrons in the outer shell is considered full and a new energy level appears with the next element Draw the Bohr diagram for Sodium, Chlorine, and Calcium Lewis Dot Structure Only draw the number of valence electrons around the symbol The group number tell you how many valence electrons are around the atom Draw the Lewis Dot structure for Calcium, Carbon, and Hydrogen Compounds Compound- a pure substance that is made up of one or more elements i.e. H 2 O ( is 2 hydrogen and 1 oxygen) Compounds form to create stable atoms 2 bond types we are covering Covalent Bonds- a bond formed by the sharing of electrons Ionic Bond- a bond formed by the attraction of two oppositely charged ions 4

5 The water molecule formed by covalent bonds. has 10 protons and 10 electrons, but the molecule it is slightly polar Polarity- uneven distribution of charges The polarity of water is what makes it so important to life Hydrogen Bonding Bond that forms when hydrogen atoms have a slightly positive charge in a molecule and are attracted to a slightly negative charge in another molecule molecule can have up to 4 hydrogen bonds giving water several special properties Properties Cohesion- the attraction between molecules of the same substance n molecules like to stick together n Reason water forms beads on certain surfaces 5

6 Properties Adhesion- attraction between molecules of different substances n If the other substance is polar, water will stick to it n Capillary action where water rises in a narrow tube against gravity Properties Temperature Moderation n takes longer to heat because the hydrogen bonds absorb the energy first until they are broken n Only when all the bonds are broken does the temperature rise 6