Life depends on chemistry... Because chemical compounds are the building blocks of life. A. Chemistry = study of the composition, structure, properties, and reactions of a substance. **Discovery Streaming Clip** Matter: Building blocks of the Universe

 NOTE: MASS= The quantity of matter an object has. MASS AND WEIGHT ARE NOT THE SAME! Mass vs. weight animation

1. Definition= basic unit of matter 4. Electrons move about the nucleus. The # of electrons is equal to the # of protons. 2. Atoms are composed protons(+), neutrons(0), and electrons(-) 3. Protons and neutrons are located in a central area called the nucleus.

2. About 96% of the mass of all kinds of living things is composed of a combination of just 4 elements… 1. Definition = a pure substance that contains only one type of atom

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3. Periodic Table—developed as a way to organize elements Trends in periodic table  Elements are found in order of atomic number (# of protons)  Atomic weight (# of protons + # of neutrons) get bigger as you go across and down  Periods of elements = rows ---As you go across a row, elements get smaller in size BUT greater in mass ---Example: The go from a beach ball to a bowling ball  Groups of elements = columns Elements in the same group have similar properties and will bond in similar ways

PERIODIC TABLE GROUPS/FAMILIES PERIOD Atomic size decreases and atomic mass increases As you go L to R across a period

Information gathered from the PERIODIC TABLE 2 He Helium 4 Atomic Number Chemical Symbol Element Name Atomic Mass ***Element Song*** **Harry Potter Elements Song**

2. Remember mass number = number of protons plus neutrons in nucleus of atom Example: carbon-12, carbon-13, carbon-14 Carbon – 12Carbon – 13Carbon – 14 # protons # neutrons

Go to element exploration...

MOST elements do not exist by themselves Definition : a substance formed by the bonding of two or more elements in definite proportions  Examples: H 2 O, NaCl, CO 2 2. Chemical formula = shows the composition of the compound 3. physical and chemical properties of compound are DIFFERENT from each element alone

G. Bohr Models of Atoms 1 st electron shell can hold—2 electrons 2 nd electron shell can hold—8 electrons 3 rd electron shell can hold—8 electrons  Examples: Hydrogen (1) Carbon (6) Oxygen (8) Chlorine (17)

1. Definition= the forces that hold together the atoms that make up compounds 2. Two main types of STRONG chemical bonds: 1= ionic bonds 2= covalent bonds... Let’s take a look at each type more closely....

---a TRANSFER of electrons takes place resulting in ions ---ion = a positively or negatively charged atom ---ions of opposite charge attract strongly, thus forming an ionic bond 1. Ionic bonds

The number of electrons in outer energy shell determines the chemical properties of an atom. **Atoms want their outermost shell to be full** Example: NaCl

When sodium chloride (NaCl) is formed, one electron from sodium is transferred to chlorine.

**Ionic Demo**

---involves SHARING of electrons ---single covalent bond = share one electron ---double covalent bond = share two electrons...etc. --result of covalent bond = a molecule... which is the smallest unit of a compound --Example: Methane (CH 4 ) 2. Covalent bonds **Covalent Demo** click through tutorial reading 1-14, 22-24, and 30

In a double bond, 2 atoms share 2 pairs of electrons (4 electrons)

In a triple bond, 2 atoms share 3 pairs of electrons (6 electrons)

Sharing of electrons between two Oxygen atoms

Structure of the 4 elements that make up most of the mass of living things: