The Chemistry of Life (from Biology: Principles and Explorations) Atomic Structure The Periodic Table “Happy Atoms” Chemical Bonds Lewis Dot Diagrams

Matter is made of atoms Atom- the smallest unit of matter that can’t be broken down by chemical means Composition: 1. Nucleus- made of protons (+) and neutrons (no charge) 2. Electron cloud- region of atom where electrons (-) are found orbiting the nucleus in electron shells *FYI: Because protons and electrons are oppositely charged, they attract one another. *FYI: Usually there is one p+ for every e- so they have no electrical charge

An element is a substance made of only one kind of atom. Each element is represented by a 1, 2 or 3 letter symbol. Most elements occur naturally in nature, some are man made. But, they can all be found on the periodic table.

What do the numbers and letters mean in each element box? FYI: AMU = # of protons + # of neutrons

The periodic table is organized into a big grid. The elements are placed in specific places because of the way they look and act. Each row is a PERIOD. All elements in the same row have the same number of electron shells.

The periodic table is organized into a big grid. Each column is a GROUP. All elements in the same column have the same number of electrons in their outer shell (usually indicated by the roman numeral at the top of each column). *FYI: Elements that are in the gray area, called transition elements, have special electron rules which you will learn when you take physical science and chemistry.

Review Quiz! 1) What is the “smallest unit of matter that can’t be broken down by chemical means” called? 2) Which 2 subatomic particles are found in the nucleus of an atom? 3) What subatomic particle is found orbiting the nucleus in shells? 4) Rows in the periodic table are called what? 5) Elements in rows have the same number of _____ _____. 6) Columns in the periodic table are called what? 7) Elements in columns have the same number of _____ shell electrons. 8) What does the atomic number tell you about an element?

What is a “Happy Atom”? Electrons orbit the nucleus of an atom in energy shells (a.k.a., orbitals or electron shells). An atom is “happy” when its outer shell is full. Some atoms have too many electrons and want to give them away, like sodium (Na) or Magnesium (mg).

What is a “Happy Atom”? Some atoms have too few electrons and would like to receive some more, like Oxygen (O) or Fluorine (Fl)).

How many electrons does a shell have to have to be “happy”? The 2-8-8 rule: The 1st shell is full (or “happy”) with 2 electrons in it. Exception: Hydrogen (H) is happy with 1 electron The 2nd is full with 8 electrons. The 3rd is full with 8 electrons (for the first 18 elements)

How do atoms get or get rid of electrons so they can be “happy”? There are a couple of ways atoms can get the electrons they want so they can be “happy”. 1) They can share electrons with one or more atoms or 2) they can “borrow” them from one or more atoms This is how atoms bond together to make molecules!                                                                                                                              

What are the two kinds of chemical bonds called? 1) Covalent bonds- occur when two or more atoms share electrons to form a molecule *FYI: the charge on the molecule is neutral (i.e., no charge)

Atoms can bond together Ionic bonds- occur when atoms give or receive one or more electrons

Review Quiz! What do the pink and blue circles around the nucleus represent? What do the numbered dots on the rings represent? Is this atom “happy”? How do you know? What would make this atom “happy”? What two kinds of bonds could help make this atom “happy”?

Is there a simple diagram I could use to draw atoms and their shells? Yes! Its called a Lewis Dot Diagram! 1st, determine the number of electrons in the outer shell of the element you want to diagram-do you remember how to do this? 2nd, write the element symbol and pretend it’s a clock. 3rd, place a dot (which represent an electron) at 12, 3, 6, 9 o’clock and so on until you’ve shown all electrons in the outer shell of that element. *FYI: Always place dots one at a time, going clockwise around the element symbol. There should never be more than two dots at 12, 3, 6 and 9 o’clock.