Sodium Chlorine Sodium chloride

1

Reactants Reaction Products

2 H2 2 H2OO2+

2

3

Nucleus

Protons (+ charge)determine element

Neutrons (no charge)determine isotope

Electrons (– charge)form negative cloudand determinechemical behavior

Atom

4

Cloud of negativecharge (2 electrons)

Electrons

Nucleus

(a) (b)

5

A ball bouncing down a flightof stairs provides an analogyfor energy levels of electrons.

Third shell (highest energylevel in this model)

Second shell (higherenergy level)

First shell (lowest energylevel)

Atomic nucleus

Energyabsorbed

Energy lost

(b)

(a)

6

Electronorbitals

7

Neon, with two filledShells (10 electrons)

First shell

Second shell

First shell Second shell

1s orbital 2s orbital Three 2p orbitals

(a) Electron distribution diagram

(b) Separate electron orbitals

(c) Superimposed electron orbitals

1s, 2s, and2p orbitals

x y

z

8

First shell

Second shell

Third shell

Hydrogen

1H

Lithium

3Li

Sodium

11Na

Beryllium

4Be

Magnesium

12Mg

Boron

5B

Aluminum

13Al

Carbon

6C

Silicon

14Si

Nitrogen

7N

Phosphorus

15P

Oxygen

8O

Sulfur

16S

Fluorine

9F

Chlorine

17Cl

Neon

10Ne

Argon

18Ar

Helium

2He2

He4.00Mass number

Atomic number

Element symbol

Electrondistributiondiagram

9

+ –

NaSodium atom

ClChlorine atom

Na+

Sodium ion(a cation)

Cl–

Chloride ion(an anion)

Ionic bond

Electronictransferforms ions

10

Na+

Cl–

11

Hydrogen atoms (2 H)

Hydrogen molecule (H2)

12

Singlecovalent bond

Doublecovalent bond

13

(a) Hydrogen (H2)

(b) Oxygen (O2)

(c) Water (H2O)

Name andMolecularFormula

ElectronDistribution

Diagram

Lewis DotStructure and

StructuralFormula

Space-FillingModel

(d) Methane (CH4)

14

H H

H2O+ +

–

O

15

Water (H2O)

Ammonia (NH3)

Hydrogen bond

–

–

+

+

+

+

+

16

s orbital Three p orbitalsFour hybrid orbitals

Tetrahedron

(a) Hybridization of orbitals

z

x

y

Space-FillingModel

Ball-and-StickModel

Hybrid-Orbital Model(with ball-and-stick

model superimposed)

UnbondedElectronpair

Water (H2O)

Methane (CH4)

(b) Molecular-shape models

17

Natural endorphin

Morphine

Carbon

Hydrogen

Nitrogen

Sulfur

Oxygen

(a) Structures of endorphin and morphine

(b) Binding to endorphin receptors

Brain cell

MorphineNaturalendorphin

Endorphinreceptors

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