Download Chemical Bonds

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You need to study your notes and vocab.
Make sure you know the following things:
 What is a period? What does it represent?
 What is a family? What does it represent?
 What is atomic mass?
 If you know the atomic number and atomic mass,
what else do you know?
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Selenium’s (Se) atomic number is 34. Its atomic
mass is 79. Its period is 4, its family is 6.
On your paper, answer the following questions:
1. How many protons does Se have?
2. How many electrons does Se have?
3. How many neutrons does Se have?
4. How many orbitals does Se have?
5. How many electrons are in its outer orbital?
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C2.a
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Atoms in
compounds are
held together by
bonds.
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This is where
electrons become
important…
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The octet rule states that elements gain or
lose electrons to attain an electron
configuration of the nearest noble gas.
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Valence electrons are electrons that are
available to form bonds.
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They are the electrons furthest to the outside
of the atom (outer orbital).
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The electrons that are the nearest to the
nucleus are held more tightly than those
farther away and cannot leave orbit.
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Remember when I said atoms like to have
equal numbers of protons and electrons.
Well… that’s not always the case…
An ion is an atom or molecule with a net
electric charge (either positive or negative)
due to the loss or gain of one or more
electrons.
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An atom that gains an electron has a
negative charge.
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An atom that loses an electron has a
positive charge.
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An ionic bond is a bond formed when
electrons are transferred from one atom to
another (gain/lose e-); the attraction between
oppositely charged ions.
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Usually when metals bond with nonmetals.
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A covalent bond forms when electrons are
shared between atoms.
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Usually when nonmetals bond together.
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Not actually a bond.
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Chemical attraction in which the proton of a
hydrogen atom of one molecule is attracted to
an electronegative atom of another molecule.
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Think H2O (water).
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These bonds are weaker attractions than
covalent or ionic bonds.
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Hydrogen bonds have to involve hydrogen.
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Will also involve an electronegative atom such
as N (nitrogen), O (oxygen), or F (fluorine).
C2.a
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A chemical reaction involves either the
making or breaking of chemical bond.
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This is a process that changes one set of
chemicals into another set of chemicals.
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These occur slowly:
 Iron + Oxygen -> Iron Oxide (rust)
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Or they can occur quickly:
 Hydrogen gas + Oxygen -> EXPLOSION
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The elements or compounds that enter into a
chemical reaction are called reactants.
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The elements or compounds that are produced
by a chemical reaction are called products.
Reactants
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H2O + CO2 -> O2+ C6H12O6
Products
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Law of Conservation of Energy: energy can
neither be created nor destroyed…
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So energy is released or absorbed whenever
a chemical bonds are broken or formed.
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Since atoms aren’t typically destroyed or
created, you must have the same number of
an element before and after a chemical
reaction occurs.
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This is called balancing chemical equations.
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Subscripts: little numbers; come after the
element; represent the number of atoms of
that elements; CANNOT be changed.
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Coefficients: big numbers; come at the
beginning of an element or compound; think
multiplication; CAN be changed.
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Add coefficients in front of the compounds to
balance the following equation:
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H2O + CO2 -> O2+ C6H12O6