Bond… Chemical Bond

Chemical Bonds Chemical bonding is the joining of atoms to form new substances.

Most of the things you come in contact with are combinations of atoms plastic salt sugar milk chocolate wood Just as the 26 letters of the alphabet combine to make words, the elments combine to form compounds air water cotton caffeine

Valence Electrons A valence electron is an electron in the outermost energy level of an atom, which causes bonding.

Valence Electrons Carbon 4 valence electrons Beryllium 2 valence Oxygen 6 valence electrons

Valence Electrons *Atoms of elements in Groups 1 and 2 have the same number of valence electrons as their group number. *Atoms of elements in Group 3-12 do not have a general rule relating their valence electrons to their group number. However, they typically have between 1 or 2 valence electrons. *Atoms of elements in Groups 13-18 have 10 fewer valence electrons than their group number. (Exception - helium atoms have only 2 valence electrons, even though they are in group 18)

Octet Rule Atoms will combine to form compounds in order to reach eight electrons in their outer energy level.

The Octet Rule In Action 6 7 Notice how this chlorine atom has seven valence electrons, one away from eight. It will try to gain one more according to the Octet Rule. 5 + - 4 1 1 2 3 Notice how the sodium atom has one valence electron. It is this electron that it will try to get rid of according to the Octet Rule. Where do you think chlorine finds that one electron that it needs?

Pop Quiz Question #1 Which shell is the valence shell? First Second Middle Last

Pop Quiz Question #2 Which element has 5 valence electrons? A. chlorine B. nitrogen C. oxygen D. hydrogen

Writing Chemical Formulas A chemical formula uses chemical symbols to represent the atoms of the elements and the amount of each atom in a chemical combination Carbon dioxide carbon + oxygen + Carbon dioxide C O A subscript is a number written to the right of a chemical symbol and slightly below it. It tells how many atoms of each element are in the combination CO2  C + O + O

Pop Quiz Question #3 When sodium bonds with oxygen, they form A. Na3O2 B. Na2O3 C. Na2O D. NaO

Pop Quiz Question #4 How many atoms are H2SO4? A. 4 B. 5 C. 6 D. 7

Types of Chemical Bonds Co-captain? What does the word cooperate mean? Coworker? So, the prefix “co-” means . . . share The first type of chemical bond is called a covalent bond Covalent bonds occur when atoms share electrons

COVALENT BOND Each pair of shared electrons creates a bond Usually occurs between atoms of non-metals Consequently, neither atom is "strong" enough to steal electrons from the other, so they have to share electrons - - - - + - + + - - - - -

Types of chemical bonds The second type of chemical bond is known as ionic bonds Ionic bonds occur when atoms transfer electrons

IONIC BONDS The force of attraction between oppositely charged ions. Usually form between atoms of metals and atoms of non-metals Consequently, the non-metal is "stronger" than the metal, and can steal electrons very easily from the metal. Resulting compounds have a name that usually ends in –ide 1- 1+ Cl Na Which different groups or families of elements will most-likely interact to create these types of bonds? -

Covalent Ionic Compounds Compounds Gases, liquids, or solids Low melting and boiling points Poor electrical conductors Most are not soluble in water Crystalline solids High melting and boiling points Conduct electricity when melted Many are soluble in water

how the electrons do not just stay with one ion Metallic Bond A force of attraction between a positively charged metal ion and the electrons in a metal Many metal ions pass along many electrons Many properties of metals, such as conductivity, ductility, and malleability, result from the freely moving electrons in the metal Usually occurs between atoms of metals Al3+ - This is why metals are able to conduct heat and electricity. - - Notice how the electrons do not just stay with one ion - - - - - - - - - - -

Which bond is formed from the transfer of electrons? Pop Quiz Question #5 Which bond is formed from the transfer of electrons? A. Ionic B. Covalent C. Metallic