Atoms are the smallest components of an element that still retains all of the chemical properties of an element.
Atoms contain three subatomic particles: protons, neutrons and electrons.
- Protons: have a positive charge and are located in the nucleus
of an atom
- Neutrons: have no charge and are located in the nucleus of an
atom
- Electrons: have a negative charge and are located
surrounding the nucleus in electron shells
Matter occupies space and has mass. All matter is composed of elements, substances that cannot be broken down or transformed chemically into other substances. Each element is made of atoms.
Valence electrons are the electrons in the outermost shell of an atom.
Atoms will fill their innermost shell, the one closest to the nucleus, with electrons first. This first shell can hold up to 2 electrons. All other shells can hold up to 8 electrons. Atoms seek to have their outer shell full of electrons. This is know as the octet rule, which states that with the exception of the innermost shell, atoms are more stable energetically when they have eight electrons in their valence shell.
An atom may give, take, or share electrons with another atom to achieve a full valence shell.
Ions are atoms that do not contain an equal number of positive protons and negative electrons. They are formed when atoms lose or gain electrons, giving the atom an overall charge.
Cation: Ions with a positive charge. Formed when atoms lose an electron. When an electron is lost there are now more positive protons compared to negative electrons so the overall charge of the atom is now positive.
Anion: Ions with a negative charge. Formed when atoms gain an electron. When a electron is gained there are now more negative electrons compared to positive protons so the overall charge of the atom is now negative.
In the above image sodium is forming a cation as it donates an electron and chlorine is forming an anion as it gains an electron.
Chemical Formulas: an expression that shows the elements in a compound and the relative proportions of those elements. If only one atom of a specific type is present, no subscript is used. For atoms that have two or more of a specific type of atom present, a subscript is written after the symbol for that atom
Example: C6H12O6 is glucose and it contains 6 carbon atoms, 12
hydrogen atoms and 6 oxygen atoms
Chemical Equations: the symbolic representation of a chemical reaction in the form of symbols and chemical formulas
- Reactants: the starting materials of the chemical reaction,
located on the left of the yield sign in the chemical equation
- Products: the ending materials of the chemical reaction,
located on the right of the yield sign of the chemical equation
In the above chemical equation the reactants are 2 hydrogen and one oxygen atom and the product is one molecule of water (H2O)
Ionic Bonds: Bonds that form between ions with opposite charges. For instance, positively charged sodium ions and negatively charged chloride ions bond together to make crystals of sodium chloride, or table salt.
Covalent Bonds: Bonds that form when an electron(s) is shared between two elements.
Nonpolar Covalent Bonds: forms when atoms equally share
electrons
Polar Covalent Bonds: forms when atoms unequally share
electrons, because of the unequal distribution of electrons
between the different nuclei, a slightly positive (δ+) or slightly
negative (δ–) charge develops
Hydrogen Bonds: This bond is a weak interaction between the δ+ charge of the hydrogen atom of one molecule and the δ– charge of the other molecule.
When polar covalent bonds containing a hydrogen atom form, the hydrogen atom in that bond has a slightly positive charge. This is because the shared electron is pulled more strongly toward the other element and away from the hydrogen nucleus. Because the hydrogen atom is slightly positive (δ+), it will be attracted to neighboring negative partial charges (δ–).
Metabolism is all the chemical reactions occurring in a living organism.
Metabolism = anabolism + catabolism
Anabolism: the synthesis of complex molecules from simpler
ones
Catabolism: the breakdown of complex molecules to form
simpler ones
The following will increase the rate which a reaction will occur:
- An increase in the number of reactants
- An increase in temperature
- The presence of a catalyst
The pH of a solution indicates its acidity or basicity.
The range goes from 0 - 14, with 7 being neutral.
The closer to 0 the more acidic, the closer the 14 the more basic
Acids will donate hydrogen ions (H+) to solution while bases will donate hydroxyl ions (OH-) to solution
Buffer: A solution that resists changes in pH
