Chemical Molecules (October 23rd)

What is the difference between Atomic Number and Atomic Mass?

It has to do with the number of protons

Atomic Number

Refers to the number of protons

Atomic mass

Refers to the total mass of protons, neutrons, and electrons

Mass number =

number of protons + neutrons

To calculate the number of neutrons in an element…

subtract the atomic number from the atomic mass

Isotopes

Forms of an element with different number of neutrons, and so have different mass numbers

Molecules

are formed when two or more atoms join by bonds

Compounds

atoms of more than 1 element held by bonds

Having a Carbon on a molecular formula makes it….

an Organic molecule

Isomers

same molecular formula, but different molecular structures

Enantiomer

Isomers that are mirror images of each other

Bohr Model

an early model with protons in the nucleus and electrons in orbit

Orbits

Electron shells or energy levels

Electrons fill orbitals closest to the nucleus…..

first

Octet Rule

an atom will gain, lose, or share electrons in order to achieve a stable configuration of 8 electrons in outermost shell

Outer shell=

Valence shell

Reactions

substances used at the beginning of a reaction

Products

the substances formed at the end of the reaction

Chemical Reactions can be….

reversible or irreversible

Irreversible reactions

proceeds in one direction until all reactants are used up

Reversible Reactions

a reaction in which the conversion of reactants to products and the conversion of products to reactants occur simultaneously

Chemical Bonds:

Covalent bonds

Iconic bonds

Hydrogen bonds

Hydrophobic bonds

van der Waals interaction

Covalent bonds

Electrons are shared in a pairs of single, double, or triple bonds

Nonpolar bond

equal sharing of pairs of electrons

Polar bonds

Unequal sharing of polar bonds

Electronegativity

attraction force that an atomic nucleus exerts on electrons in a covalent bond

Subtract electronegativity of the two atoms for the difference:

nonpolar: less than or equal to 0.5

polar: greater than 0.5

the atom with the larger number of electronegativity has….

more electrons

Ionic bonds

atoms give up or gain electrons

Cation are positive

Anions are negative

Cations give up to Anions in…..

Ionic bonds