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Matter, Elements,and Compounds
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- MATTER: anything that
takes up space and has mass.
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- ELEMENT: a substance
that cannot be broken down by ordinary means. The material
making up matter.
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- There are 92 naturally occurring elements,
of these 25 are essential to life. 4 of these make up
96% of living matter ( Carbon, Hydrogen, Oxygen,and
Nitrogen). The rest are called trace elements. These
are required in minute amounts( Zinc, cobalt, iron,
magnesium).
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- Small units of matter are called atoms.
Protons(+), neutrons(0),
and electrons(-), are the
subunits of atoms. Their mass is measured in units called
Daltons.
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- ATOMIC NUMBER: THE TOTAL NUMBER
OF PROTONS IN AN ATOM.
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- ATOMIC MASS: THE TOTAL NUMBER
OF NEUTRONS AND PROTONS IN AN ATOM.
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- ISOTOPES: Different atomic forms
caused by varying the number of neutrons.
- Example: Normal carbon is 12, carbon
isotope is 14.
- Some isotopes are radioactive, they
undergo a transformation to gain a stable condition.
This transformation is called the half-life of the isotope.
Example: Let's say the half-life of carbon 14 is 5,000
- years, If we have 100g. of carbon 14
now, in 5000 years will have 50g. In 10,000 years we
will have 25g. etc.
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- ENERGY LEVELS: All electrons
have the same mass and charge. They differ in the amounts
of potential energy they possess. Electrons closer to
the nucleus contain less potential energy. The farther
away from the nucleus the more potential energy they
contain.
- These different states of potential
energy are called energy levels.
- Each level is divided into subunits
called orbitals. No more than 2 electrons can occupy
the same orbital.
- The 1S orbital (closest to nucleus)
contains 2 e-
- The next level is divided into 4 orbitals.
S and 3p orbitals for a total of 8 electrons.
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- Valence electrons: These electrons
occupy the last energy level of an atom. It is here
where atoms come in contact with each other. It stands
to reason that chemical bonds will occur here in any
chemical reaction. The maximum number of valence electrons
any atom can contain is 8. Any number less than 8 will
allow that atom to act as a donor or recipient of electrons
to become stable. Atoms that give electrons will become
+ ions and have a + charge, while atoms that receive
electrons will become a negative ion with a - charge.
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- Chemical Bonding: Atoms will
interact with each other depending on their incomplete
valence shell.
- There are several types of chemical
bonds:
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- Covalent Bond: These bonds are
the strongest of the bonds. They are formed by the sharing
of the valence electrons. There are several subsets
of covalent bonding:
- a). Nonpolar: Here the valence electrons
are shared equally, thus eliminating a positive
and negative end on the molecule.
- 1). double nonpolar: O2
- 2). triple nonpolar: N2
- b). Polar covalent bond:
Here the valence electrons are shared unequally,
causing the molecule to develop a positive end (
where the electrons spend less time) and a negative
end( where the electrons spend more time). This
has to do with the electronegativity of the atom.
The more electronegative the atom the more it will
hold on to the electrons. Oxygen is very electronegative.
Hydrogen is not.
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- Ionic Bond: These bonds are
formed by the taking of electrons. Anion: negative ion,
Cl- and (OH) Cation: positive ion, Na+
and (NH4)+.
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- Other Bonds
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- Hydrogen Bond: This bond is
formed when Hydrogen that is covalently bonded to an
electronegative atom is attracted to another electronegative
atom on another molecule.
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- van der Walls interactions:
These are nonpolar bonds caused by accumulations of
+ or - charges at the ends of molecules. These are transient
forces, and change rapidly.
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- Hydrophobic interactions: oil
forming droplets that seal out water.
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- Chemical Reactions: The combination
of 2 or more elements forming a different product or
products. Each reaction contains reactants and products.
The reactants are written on the left side of the equation,
while the products are written on the right side. The
reactants and products must contain the same number
of atoms making the reaction balanced.
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- Click here to link up with an interactive
periodic
table of elements.
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