Sodium Chlorine Sodium Chloride

1 2 H2 + O2 2 H2O

Reactants Reaction Products

2 3 Nucleus

Protons (+ charge) determine element Electrons (– charge) form negative cloud and determine Neutrons (no charge) chemical behavior determine isotope Atom

4 Cloud of negative Electrons charge (2 electrons) Nucleus

(a) (b)

5 (a) A ball bouncing down a flight of stairs provides an analogy for energy levels of electrons.

Third shell (highest energy level in this model)

Second shell (higher Energy energy level) absorbed

First shell (lowest energy level) Energy lost Atomic nucleus (b) 6 Electron orbitals

7 First shell Neon, with two filled Shells (10 electrons) Second shell (a) Electron distribution diagram

First shell Second shell

x y

z 1s orbital 2s orbital Three 2p orbitals

(b) Separate electron orbitals

1s, 2s, and 2p orbitals

(c) Superimposed electron orbitals 8 Hydrogen 2 Atomic number Helium He 1H He 2 Mass number First 4.00 Element symbol shell Electron distribution diagram Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon

3Li 4Be 5B 6C 7N 8O 9F 10Ne Second shell

Sodium Magnesium Aluminum Silicon Phosphorus Sulfur Chlorine Argon

11Na 12Mg 13Al 14Si 15P 16S 17Cl 18Ar Third shell

9 Ionic bond

+ – Electronic transfer forms ions

Na Cl Na+ Cl– Sodium atom Chlorine atom Sodium ion Chloride ion (a cation) (an anion)

10 Na+ Cl–

11 Hydrogen atoms (2 H)

Hydrogen molecule (H2) 12 Single Double covalent bond covalent bond

13 Name and Electron Lewis Dot Space- Molecular Distribution Structure and Filling Formula Diagram Structural Model Formula

(a) Hydrogen (H2)

(b) Oxygen (O2)

(d) Methane (CH4)

14 δ–

H H δ+ δ+ H2O

15 δ– δ+

Water (H2O)

δ+ Hydrogen bond δ–

Ammonia (NH3)

δ+ δ+

δ+ 16 z Four hybrid orbitals s orbital Three p orbitals

Tetrahedron (a) Hybridization of orbitals

Space-Filling Ball-and-Stick Hybrid-Orbital Model Model Model (with ball-and-stick model superimposed) Unbonded Electron pair

Water (H2O)

Methane (CH4)

(b) Molecular-shape models 17 Carbon Nitrogen Hydrogen Sulfur Natural endorphin Oxygen

Morphine

(a) Structures of endorphin and morphine

Natural endorphin Morphine

Endorphin Brain cell receptors

(b) Binding to endorphin receptors 18