Chemical Bonding

How do elements combine to form compounds?

Chemical Bonds- Force of attraction that holds 2 or more elements together

Octet Rule = atoms tend to gain, lose or share electrons so as to have 8 valence e’s C would like to N would like to O would like to Gain 4 electrons Gain 3 electrons Gain 2 electrons

Chemical bonds: an attempt to fill electron shells Some types of bonds are: Ionic bonds – transfer e’s; metal to non-metal Covalent bonds – share e’s; 2 non-metals Metallic bonds – e’s flow from metal atom to metal atom

IONIC BOND- Bond formed between two ions by the transfer of electrons from a metal to a non-metal.

Metals usually have <4 valence e’s so lend e’s Non-metals usually have >4 valence e’s and borrow e’s

Review Ionic Bonds – show transfer of electrons from metal to nonmetal -Metals give up valence electrons (to see 8 in lower shell. -Nonmetals receive electrons (enough to see 8 valence e’s The result is the formation of positive and negative ions that are bonded by electrostatic attraction

Ionic Compounds -High melting and boiling pts Ionic Compounds -High melting and boiling pts. -Crystal lattice -Form electrolytes when dissolved in water (conduct electricity) -solid at room temp.

REVIEW QUESTIONS What part of the atom is involved in ionic bonding? Ionic compounds are made of one element that is a __________ and one element that is a ____________. What is an ion? Valence electrons metal nonmetal A charged particle

REVIEW QUESTIONS give up 4. Metals will _______ electrons and become ions with a __________ charge. 5. Non metals will _______ electrons and become ions with a ________ charge. 6. An ion with a +3 charge means the atom has _________________ electrons. positive receive negative given up 3

REVIEW QUESTIONS 7. An ion with a -2 charge means that the atoms has _______________ electrons. 8. The formula for potassium chloride would be ______________. received 2 KCl

Show bonding animation: http://www. youtube. com/watch

COVALENT BOND bond formed by the sharing of electrons

Covalent Bond Between two or more non-metals. Formed by sharing electron pairs # of bonds = the number of valence e’s needed to total 8.

Covalent Compounds -Low melting pts and b. p Covalent Compounds -Low melting pts and b.p. -Solids, liquids and gases at room temp -Non-electrolytes

Covalent Bonds

2. Covalent bonds- Two atoms share one or more pairs of outer-shell electrons. Oxygen Atom Oxygen Atom Oxygen Molecule (O2)

lets look at the molecule Cl2 - lets look at the molecule Cl2 Cl Cl Cl + Shared Electrons

Hydrogen is happy with 2 electrons. - H H O 2 O H H H Hydrogen is happy with 2 electrons.

- N Nitrogen has three spots for bonding, and shares three pairs of electrons.

Each nitrogen has a set of electrons that are not available for bonding. Nitrogen can only make 3 bonds. N N These triple bonds are very strong, and have a very high bond energy. therefore it is a very stable bond.

Lewis Dot Diagrams, used to represent covalent bonds Can also use lines to represent bonds There are three types of bonds, single, double, and triple.

- H H SINGLE DOUBLE N TRIPLE N

Ionic vs. Covalent Bonds Ionic Bonds Form when electrons are exchanged between atoms. Form between a metal and a non-metal. Covalent Bonds Form when electrons are shared between atoms. Form between two non-metals. Both types of bonds result in all atoms having a full outer energy level.

Ionic Compounds Covalent Compounds High m.p., b.p Low m.p., b.p. Solid at room temp Solid, liquid, gas at room temp. Dissolved in water: electrolytes Dissolved in water: non-electrolytes

Practice State type of bond: NaCl; Ionic Bond C2H6; Covalent Bond Na(CO3)2; Ionic & Covalent

METALLIC BOND Force of attraction between positively charged metal ions and the electrons in a metal.

Metallic Bond, A Sea of Electrons

Metallic Bond Formed between atoms of metallic elements Valence electrons flow from one atom to the next and form a combined electron cloud around atoms Good conductors at all states, lustrous, very high melting points, malleable

Metals Form Alloys Metallic bonds form alloys which is a solution of a metal in a metal. Examples are Brass – mix of Cu and Zn Bronze – mix of Cu and Sn Pewter – mix of Sn, Cu, Sb

http://www.buzzfeed.com/jessicamisener/extremely-freaky-chemical-physical-reaction-gifs

Credits education.jlab.org/jsat/powerpoint/chembond.ppt