Biology 12

Chapter 1 The Chemistry of Life • MHR 9

Na+

CI−

11p

12n

11p

12n

17p

18n

17p

18n

Na Cl

sodium chloride

NaCl

11p

12n

17p

18n

17p

18n

11p

12n

one electron in outermost

occupied shell

electron

given up

electron

accepted

sodium atom (Na) sodium ion (Na+)

8 electrons in outermost

occupied shell

11 protons (+)

10 electrons (−)

one

+ charge

=

17 protons (+)

18 electrons (−)

one

− charge

=

7 electrons in outermost

occupied shell

chlorine atom (Cl) chloride ion (Cl−)

8 electrons in outermost

occupied shell

arrangement of sodium

and chloride ions in one

salt crystals salt crystal

1 mm

Ionic Bonding

Figure 1.4Reaction between sodium and chlorine to form ionic sodium chloride

When a sodium atom gives up an

electron, it becomes a positive ion.

A

When a chlorine atom gains an

electron, it becomes a negative ion.

B

When sodium reacts with chlorine,

sodium chloride (NaCl) is formed.

C

In a sodium chloride crystal, ionic

bonds between Na+and CI−create

a three-dimensional lattice. Each

sodium ion is surrounded by six

chloride ions, and each chloride ion

is surrounded by six sodium ions.

D