Chemical Bonding Valence Shells, Ionic Compounds, Molecular Compounds, Chemicals in Your Life

Chemical Families and Trends The way in which elements come together to form compounds is based on their electron configurations –Bohr-Rutherford Model will provide us with a great model to work with

Parts of an Atom Protons – are positively charged and have mass Neutrons – are neutral in terms of charge an have mass. Electrons – are negative and have relatively no mass

Chemical Families Noble Gases – unreactive –Modern light bulbs are filled with argon so the tungsten filament will not react with oxygen and burn out –Eight electrons in the outer shell is called a stable octet Halogens – one electron short of stability –Want to gain an electron to make a stable octet and will react with everything to try to achieve this

Chemical Families Alkali Metals – one electron beyond stability – Wants to get rid of extra electron to reach stability –The most reactive alkali metal atoms are the largest –Sodium wants to shed one electron What is it’s electron configuration like now?

Chemical Families Alkaline Earth Metals – two electrons beyond stability –Will react vigorously but not as vigorous as the alkali metals (group 1) –Most reactive are the largest ones –Two fluorine atoms would be needed to react with one magnesium Two electrons need to be discarded

Ionic Compounds Stable Octets – NaF –Sodium can obtain a stable octet by releasing one of it’s electrons and fluorine can do the same by gaining an electron –Both will lose original properties though Fluorine will have a negative charge Sodium will have a positive charge Alkaline Earth Metals? –Need to get rid of two electrons, how will that change the number of fluorine atoms that it will bind to?

Ionic Compounds Ion – when an atom gains or loses an electron Think about sodium…what if it were to lose one electron? Think about fluorine…what if it were to gain one electron? This has everything to do with how ionic bonding occurs ionic bondThe positive ions are attracted to the negative ions and this creates an ionic bond Electrons in outer shell are called valence electrons and this number is the same for all elements in a group –Lithium and oxygen example –Magnesium and oxygen example

Ionic Compounds One common way to identify ionic compounds is that they are formed between metals and non-metals Why would this hold true? Ions in an ionic compound will fit together in a regular repeating pattern known as a crystal lattice –Not electrical conductors but when dissolved the ions come loose and they are excellent conductors

Molecular Compounds Uncharged atoms come together to form compounds Ionic compounds are formed when electrons are swapped (exchanged) however molecular compounds are based on the idea of sharing electrons –TWO NON METALS covalent bondThis electron sharing is known as a covalent bond

Molecular & Ionic Compounds What is the difference? Covalent Bonds Bonding between atoms is strong however the attraction between molecules is weak Low attraction between molecules means low melting and boiling points TWO NON METALS

Molecular & Ionic Compounds Ionic Bonds –Strong attraction between molecules are it behaves like one large structure –METAL + NON METAL

Physical Properties Colour and lustre – the light a substance reflects and its shininess. Conductivity – ability of a substance to conduct heat to electricity. Hardness – ability to hold its shape or be scratched. Texture – how it feels or looks Solubility – ability of substance to dissolve in water.

Chemical Properties Reaction with acid – when substances react with acid often a gas is formed demonstrating a chemical change. Reaction with water – same as above. Reaction with iodine – when starches react with iodine there is a colour change from yellow to purple