CHEMISTRY Chapter 2

A. Chemistry = study of the composition, structure, properties, and reactions of a substance. Life depends on chemistry . . . Because chemical compounds are the building blocks of life.

MASS AND WEIGHT ARE NOT THE SAME! B. MATTER =Anything that takes up space and has mass Mass vs. weight animation NOTE: MASS= The quantity of matter an object has. MASS AND WEIGHT ARE NOT THE SAME!

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

D. ELEMENTS CARBON-C HYDROGEN-H OXYGEN-O NITROGEN-N 1. Definition = a pure substance that contains only one type of atom 2. About 96% of the mass of all kinds of living things is composed of a combination of just 4 elements… CARBON-C HYDROGEN-H OXYGEN-O NITROGEN-N

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Columns, rows, noble gases? PERIODIC TABLE EXPLORATION How is it arranged? Any patterns? Columns, rows, noble gases?

3. Periodic Table—developed as a way to organize elements Elements 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

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

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

1. definition = atoms of the same element that have E. Isotopes 1. definition = atoms of the same element that have different number of neutrons 2. Remember mass number = number of protons plus neutrons in nucleus of atom Example: carbon-12, carbon-13, carbon-14 Carbon – 12 Carbon – 13 Carbon – 14 # protons 6 # neutrons 7 8

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

MOST elements do not exist by themselves. . . . . F. COMPOUNDS 1. Definition: a substance formed by the bonding of two or more elements in definite proportions 2. Chemical formula = shows the composition of the compound Examples: H2O, NaCl, CO2 3. physical and chemical properties of compound are DIFFERENT from each element alone

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

Hydrogen Carbon Chlorine Oxygen

H. Chemical Bonds 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 . . . .

1. Ionic bonds ---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

**Atoms want their outermost shell to be full** Example: NaCl Remember Rule= 2-8-8! The number of electrons in outer energy shell determines the chemical properties of an atom. **Atoms want their outermost shell to be full**

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

**Ionic Demo**

click through tutorial reading 1-14, 22-24, and 30 2. Covalent bonds ---involves SHARING of electrons ---single covalent bond =share one electron ---double covalent bond = shares 2 electrons --result of covalent bond = a molecule . . . which is the smallest unit of a compound --Example: Methane (CH4) **Covalent Demo** click through tutorial reading 1-14, 22-24, and 30

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

2 atoms share 3 pairs of electrons (6 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: