Atom
The smallest particle into which an element can be divided and still be the same element.
Electrons
Negatively charged particles that are located in the cloud around the nucleus of an atom.
Electron Cloud
The area around the nucleus where the electrons are located; does NOT show the exact number or location of electrons.
Periodic Table
Mendeleev's arrangement of the elements; still in use by chemists today.
Group (or family)
A vertical (top to bottom) of elements on the periodic table.
Valence Electrons
Electrons found in the outermost energy level of an atom.
Chemical Bond
An interaction that holds atoms or ions together.
Reactants
The elements or compounds that enter into a chemical reaction; listed on the left side of the arrow in a chemical equation.
Products
The elements or compounds produced by a chemical reaction; listed on the right side of the arrow in a chemical equation.
Bohr Model
Model of an atom that shows electrons in circular orbits around the nucleus; number of electrons IS shown.
Space-filling Molecular Model
Representation of a molecule that uses solid spheres to represent atoms and show the 3D arrangement of atoms in a molecule.
# of valence electrons group 1 elements contain
1
# of valence electrons group 2 elements contain
2
# of valence electrons group 15 elements contain
5
# of valence electrons group 18 elements contain
8
The 6 most abundant elements in the human body
Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorous, and Sulfur (C,H,N,O,P,S)
Trace Elements
Elements required by humans, but in only very small quantities
maximum # valence electrons in an atom's first shell
2
maximum # valence electrons in an atom's second shell
8
Physical Change
A change that alters the form or appearance of a material but does not make the material into another substance.
Chemical Change
A change that occurs when one or more substances change into entirely new substances with different properties.
Law of Conservation of Mass
The law that states that mass cannot be created or destroyed in ordinary chemical and physical changes.
Signs of a chemical change
Production of a new gas, Color change, Heat or Light is given off, Odor change, Solid Precipitate forms
Precipitate
A solid that forms from a solution during a chemical reaction.
Three ways an atom can form a chemical bond
Give, Take, or Share Valence Electrons
Covalent Bond
A chemical bond formed when two atoms share electrons
Ionic Bond
Formed when one or more electrons are transferred from one atom to another