MATTER: anything that takes up space and has mass.
ELEMENT: a substance that cannot be broken down by ordinary means. The material making up matter.
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).
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.
ATOMIC NUMBER: THE TOTAL NUMBER OF PROTONS IN AN ATOM.
ATOMIC MASS: THE TOTAL NUMBER OF NEUTRONS AND PROTONS IN AN ATOM.
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.
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.
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.
Chemical Bonding: Atoms will interact with each other depending on their incomplete valence shell.
There are several types of chemical bonds:
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.
Ionic Bond: These bonds are formed by the taking of electrons. Anion: negative ion, Cl- and (OH) Cation: positive ion, Na+ and (NH4)+.
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.
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.
Hydrophobic interactions: oil forming droplets that seal out water.
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.
Stoichiometry: The calculation of quantities in chemical reactions.
There are 4 ways to determine the amount of each reactant and product in each reaction.
a). Particles: React Avagadro's number of N with 3 x Avagadro's number of H to get 2 x Avagadro's number of the product.
b). Moles: 1 mole of N reacts with 3 moles of H.
c). Mass: 1 mole of N = 28 grams + 3 moles of H = 6 equals 2 moles of NH3 or 34 grams.
d). Volume: One mole of any gas occupies 22.4 L at STP. 22.4 L of Nitrogen reacts with 67.2 L of Hydrogen yields 44.8 L of NH3
Click here to link up with an interactive periodic table of elements.