Chemical Bonding

Bonds between atoms are caused by electrons in outermost shells The process of bond formation is called a reaction

The Ionic Bond Visit For 100’s of free powerpoints

Helium, neon and argon are atoms which do not react with other atoms. We call them the Inert Gases (or Noble Gases) because of this. Each of these gases has a full outer electron shell (orbit). 2p2n 10p10n18p22n He Ne Ar ,8 2,8,8

Sodium Na e.c. 2,8,1 11 protons 12 neutrons 11 electrons 11p 12n

17 protons Chlorine Cl p 18n 18 Neutrons 17 electrons e.c. 2,8,7

Na e.c. 2,8,1 (Na + ) Ion Atom e.c. (2,8) + The Sodium loses 1 electron to leave a complete outer shell. It is now a Sodium ion with a charge of 1 + The Sodium atom has 1 Electron in it’s outer shell. +

Cl e.c. 2,8,7 (Cl - ) Ion Atom e.c. (2,8,8) - The Chlorine gains 1 electron to gain a complete outer shell. It is now a Chlorine ion with a charge of 1 - The Chlorine atom has 7 electrons in it’s outer shell. -

Sodium atom Na Sodium ion (Na + ) Chlorine atom Cl Chlorine ion (Cl - ) The Ionic Bond The sodium atom loses one electron to attain a complete outer shell and become a positive ion (Na + ). The Chlorine atom gains one electron to attain a complete outer shell and become a negative ion (Cl – ). Strong electrostatic forces attract the sodium and chlorine ions. +-

Ionic Compounds Held together by strong electrostatic forces Opposite charges attract High melting points and boiling points Regular structures – giant ionic lattices When melted or dissolved ionic compounds conduct electricity

Covalent Bonding Visit For 100’s of free powerpoints

Chlorine atom 2,8,7

2 Chlorine atoms Outer shells only

Chlorine molecule Cl 2 Molecules have no overall electric charge Molecular or covalent compounds are usually gases or liquids – they have low melting points and low boiling points Forces between molecules very weak Forces (bonds) between atoms in the molecule very strong Each outer shell has 8 electrons Electrons shared

Covalent bonds can be represented in 3 ways:

Cl Chlorine Cl 2 Cl

Covalent Bonds: Water H 2 O MethaneCH 4 AmmoniaNH 3 HydrogenH 2 Hydrogen ChlorideHCl OxygenO 2 N.B. Oxygen has a double bond

Oxygen O 16 8 Oxygen atom 2,6

2 Oxygen atoms (outer shells only) Double covalent bond O O