Chemistry Review Flashcards
(27 cards)
Composition of an Atom
All matter is composed of atoms. (They are the smallest unit of matter.) Atoms are composed of electrons, protons, and neutrons.
Electrons
Negative charge, negligible mass
The Atomic Nucleus
Consists of protons (positive charge, has mass) and neutrons (no charge or “neutral,” has mass)
Atomic Number
Number of protons in an atom. (Located at the top left of an element on the periodic table)
Mass Number
Also referred to as the atomic weight (of an atom.) It is the mass of the protons + neutrons. (Located at the bottom of the element on the periodic table)
Molecule
A stable association of atoms
Molecular Weight of a Molecule
Sum of the atomic weights of all atoms in the molecule (Ex: H2O has an atomic weight of 18)
Element
A substance made from one type of atom (Ex: H2O is made of two elements, H and O, and contains three atoms (2H and 1 O))
Electrons and Chemical Bonds
The sharing of electrons between elements forms a covalent bond. The outermost electrons in an atom determine how atoms interact and their capacity to form covalent bonds (and ionic bonds.)
Electrons in the Electron Shell
An elements chemical reactivity depends on the degree to which its outermost electron shell is filled.
Electrons in the Electron Shell, Non-Reactive
Ex: Helium, Neon, and Argon have outermost electron shells which are completely full. They are non-reactive.
Electrons in the Electron Shell, Reactive
Ex: Carbon does not have a full outermost electron shell, so it can participate in covalent bonds (where it shares electrons with other atoms to fill up its electron shell)
Magnesium and Calcium
Magnesium and Calcium have 2 electrons in their outer shell, so it is easy for them to give up their electrons to another atom
Covalent Bonds
Formed by the sharing of electrons. Covalent bonds are very stable and only break with a large input of energy.
Electronegativity
Electrons in a covalent bond are most often not shared equally between the atoms. Electronegativity is the ability of an atom in a molecule to attract the shared electrons towards it’s nucleus. (Atoms with the ability to pull electrons to their nucleus are more electronegative.)
Polar Covalent Bond
One atom has greater electronegativity, so electrons in the bond are drawn more to that atom
Non-polar Covalent Bond
Electrons are shared equally (The atoms have the same or similar electronegativity.)
Polar Covalent Bond, Partial Negative and Partial Positive Charge, H2O
Ex: In H2O, the oxygen has a greater electronegativity, meaning the electrons are being pulled towards the oxygen atom. In this case, the oxygen has a partial negative charge (δ-) and the hydrogens have a partial positive charge (δ+)
Non-polar Covalent Bond, O=O
Ex: In a bond between O and O, both atoms have the same electronegativity, so the electrons are shared equally
Hydrogen Bonds (Noncovalent)
A non-covalent attraction between the δ- end of one molecule and the δ+ hydrogen of another molecule. Hydrogen bonds form between water molecules and also play an important role in the structure of DNA and Proteins. (See notebook for drawing of these interaction.)
Hydrophilic Interaction
Hydrophilic Interactions occur between polar molecules. (Molecules where electrons are not shared equally.) It means water loving, so the molecules can interact with water
Hydrophobic Interaction
Hydrophobic Interactions occur between non-polar molecules (molecules where electrons are shared equally between atoms.) It means water fearing, so these molecules can’t interact with water.
Importance of Hydrophilic and Hydrophobic Interactions
These interactions play an important role in the structure of proteins and membranes
Ionic Bonds (Non-covalent)
A non-covalent bond formed by the gain and loss of electrons. They form between charged atoms and can cause attraction or repulsion. (See notebook for drawing.)
