Bonding Covalent Ionic Metallic

Remember Lewis Dot Diagrams Symbol of the element surrounded by dots that represent valence electrons Whe atoms bond they either share or transfer electrons to complete their valence shell To draw valence electrons of atoms that are prepared to bond …

Covalent Bonding Atoms share electrons 2 electrons per bond The electrons “count” for both atoms that are being bonded together. Atoms want to be involved with 8 electrons All electrons get paired Covalent bonds form molecules Usually two nonmetals Difference in electronegativity is < 1.7

Examples F2F2 Cl 2 HCl H2OH2O NH 3 CH 4 C2H6C2H6

Examples with double / triple bonds O2O2 N2N2 C2H4C2H4 C2H2C2H2 CO 2

Other examples Remember: the central atom is the first non-H in the formula PCl 3

Energy changes in bonding Whenever any bond is formed, energy is released It takes energy to break bonds Exothermic reactions release more energy than they absorb Endothermic reactions absorb more energy than they release Triple bonds are stronger than double or single bonds. They are therefore the most stable Single bonds are the weakest covalent bonds

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Properties of Molecules Soft Low melting points Poor conductors of heat and electricity

Where do the electrons spend the most time in the bonds? Determined by the electronegativities of the atoms which are bonded together The electrons spend more time with the atom which is more electronegative When the atoms have a difference in electronegativity of 0.1  1.6 the bond is called polar No difference in electronegativity means the bond is nonpolar

How am I ever going to remember that? S ymmetrical N onpolar A symmetrical P olar

Covalent Networks Network solids Macromolecules Covalently bonded atoms are linked into a giant network throughout the entire sample.

More practice with Lewis Dot Diagrams SO 2 N 2 H 4 N 2 O 4 CCl 2 F 2 H 2 CO

Covalent bonding leads to… Covalent bonding forms molecules Properties of molecules Soft Poor conductors of heat and electricity Low melting points

Another Look at Polar and Nonpolar Bonds Look at the electronegativities Remember that polar versus nonpolar is all about the symmetry SNAP Think about the distribution of the electrons

The different types of covalent bonds There are single, double, and triple bonds Only refers to the number of electrons being shared between the two atoms 2,4,6 – can’t have any more than 6 All covalent bonds can be polar or nonpolar

The story of the mooch A type of covalent bond called “Coordinate Covalent bonding” Basically – a bond is formed where both electrons come from only one of the atoms Where do they usually come from?

The two examples of coordinate covalent bonding NH 3 + H +  NH 4 + H 2 O + H +  H 3 O + In both cases the H ion bonds to the central atom using the other atom’s electrons

Overview of covalent bonding Sharing electrons Molecules and their properties Drawing Lewis Dot Diagrams Polar vs. nonpolar SNAP Network covalent Properties Macromolecules Coordinate Covalent Mooch

The shapes of molecules Tetrahedron Trigonal pyramid Trigonal planar Bent Linear These are the only 5 options for your molecules, others exist, but you won’t see them

Other types of bonding Ionic bonding – transfer of electrons Large difference ( 1.7) in electronegativity Positive and negative ions formed by a transfer of electron(s) Metallic bonding – a sea of electrons The valence electrons are able to move around independent of their individual atoms

Lewis Dot Diagrams of Ionic Compounds Write symbol for metal and nonmetal Metal gets the charge written with it Nonmetal gets Charge Brackets Electrons Charge Write in as many as you need

Examples Draw the electron dot diagram for the compound Write the ionic formula Write the regular formula Lithium and fluorine; magnesium and sulfur; sodium and oxygen; calcium and bromine; potassium and fluorine; barium and iodine; strontium and oxygen