# GOBC

Atomic Structure

* Atoms are made up of 3 subatomic particles: protons, neutrons, and electrons* the protons and neurtons are tightly bound together to form the central portion of an atom called the nucleus* the electrons are located outside of the nucleus and thought to move very rapidly throughout a relatively large volume of space surrounding the small, but very heavy nucleus

Subatomic particles

*Protons are located in the nucleus of an atom. They carry a (+1) electrical charge and have a mass of (1) amu*Neurtons are located in the nucleus of an atom. They carry no electrical charge and have a mass of (1) amu*electrons are located outside the nucleus of an atom. They carry a (-1) electrical charge and have a mass of 1/1836 amu. (they move rapidly around the heavy nucleus)

Atomic and mass numbers

*the atomic number of an atgom is equal to the number of protons in the nucleus of the atom*Atomic numbers are represented by the symbol (Z)

Mass number of an atom

*the mass number of an atom is equal to the sum of the number of protons and neutrons in the nucleus of the atom* mass numbers are represented by the symbol (A)

Isotopes

*atoms that have the same number of protons in the nucleus but different numbers of neutrons. *they have the same atomic number but different mass numbers*Because they have the same number of protons in the nucleus, all isotopes of the same element have the same number of electrons outside the nucleus

Relative masses

*the extremely small size of atoms and molecules makes it inconvenient to use their actual masses for measurements or calculations.*They are companions of actual masses to each other.*For example: if an object had twice the mass, 2:1

Atomic Mass Unit

*a unit used to express the relative masses of atoms.*One atomic mass unit is equal to 1/12 the mass of a carbon-12 atom*A carbon-12 atom has a relative mass of 12u*An atom w/ a mass equal to 1/12 the mass of a carbon-12 atom would have a relative mass of 1u

Atomic Weight

*The relative mass of an average atom of trhe element expressed in atomic mass units*Atomic weights are the # given at the bottom of the box containing the symbol of each element in the periodic table

Molecular weight

*The relative mass of a molecule in amu *Because molecules are made up of atoms, the molecular weight of a molecule is obtained by adding together the atomic weights of the atoms in the molecule*The formula for a molecule of water is H2O. This means one molecule of hydrogen, and one atom of oxygen O. The molecular weight of water is then the sum of two atomic weights of H and the atomic weight of O.

The mole concept applied to elements

*The number of atoms in one mole of any element is called Alvogadro's number and is equal to 6.022x10 to the 23.*One mole sample of any element will contain the same numbers of atoms as a one-mole sample of any other elements*One mole of any element is a sample of the element w/ a mass in grams that is numerically equal to the atomic weight of the element